travis: Switch to Ubuntu 16.04 (xenial)

Use native packages up to llvm-6.

Reviewer: tstellar
Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

git-svn-id: https://llvm.org/svn/llvm-project/libclc/trunk@373046 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/.travis.yml b/.travis.yml
index 0c99920..37c019f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,11 +1,6 @@
 language: cpp
 
-sudo: false
-dist: trusty
-
-cache:
-  apt: true
-
+dist: xenial
 
 matrix:
   include:
@@ -15,12 +10,7 @@
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-3.9
           packages:
-            - libedit-dev
-            - g++-4.8
-            # From sources above
             - llvm-3.9-dev
             - clang-3.9
     - env:
@@ -29,12 +19,7 @@
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-4.0
           packages:
-            - libedit-dev
-            - g++-4.8
-            # From sources above
             - llvm-4.0-dev
             - clang-4.0
     - env:
@@ -43,41 +28,28 @@
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-5.0
           packages:
-            - libedit-dev
-            - g++-4.8
-            # From sources above
             - llvm-5.0-dev
             - clang-5.0
     - env:
         - LABEL="make gcc LLVM-6.0"
         - LLVM_VERSION=6.0
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
-        # llvm passes -Werror=date-time which is only supported in gcc-4.9+
-        - MATRIX_EVAL="CC=gcc-4.9 && CXX=g++-4.9"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-6.0
-            - ubuntu-toolchain-r-test
           packages:
-            - libedit-dev
-            # LLVM-6 needs libstdc++4.9
-            - g++-4.9
-            # From sources above
             - llvm-6.0-dev
             - clang-6.0
     - env:
         - LABEL="make gcc LLVM-7"
         - LLVM_VERSION=7
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
+        # llvm passes -Werror=date-time which is only supported in gcc-4.9+
         - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
       addons:
         apt:
           sources:
-            - sourceline: 'deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-7 main'
+            - sourceline: 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-7 main'
               key_url: https://apt.llvm.org/llvm-snapshot.gpg.key
             - ubuntu-toolchain-r-test
           packages:
@@ -90,11 +62,12 @@
         - LABEL="make gcc LLVM-8"
         - LLVM_VERSION=8
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
+        # llvm passes -Werror=date-time which is only supported in gcc-4.9+
         - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
       addons:
         apt:
           sources:
-            - sourceline: 'deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-8 main'
+            - sourceline: 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-8 main'
               key_url: https://apt.llvm.org/llvm-snapshot.gpg.key
             - ubuntu-toolchain-r-test
           packages:
@@ -109,12 +82,7 @@
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-3.9
           packages:
-            - libedit-dev
-            - g++-4.8
-            # From sources above
             - llvm-3.9-dev
             - clang-3.9
     - env:
@@ -123,12 +91,7 @@
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-4.0
           packages:
-            - libedit-dev
-            - g++-4.8
-            # From sources above
             - llvm-4.0-dev
             - clang-4.0
     - env:
@@ -137,41 +100,28 @@
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-5.0
           packages:
-            - libedit-dev
-            - g++-4.8
-            # From sources above
             - llvm-5.0-dev
             - clang-5.0
     - env:
         - LABEL="cmake gcc LLVM-6.0"
         - LLVM_VERSION=6.0
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
-        # llvm passes -Werror=date-time which is only supported in gcc-4.9+
-        - MATRIX_EVAL="CC=gcc-4.9 && CXX=g++-4.9"
       addons:
         apt:
-          sources:
-            - llvm-toolchain-trusty-6.0
-            - ubuntu-toolchain-r-test
           packages:
-            - libedit-dev
-            # LLVM-6 needs libstdc++4.9
-            - g++-4.9
-            # From sources above
             - llvm-6.0-dev
             - clang-6.0
     - env:
         - LABEL="cmake gcc LLVM-7"
         - LLVM_VERSION=7
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
+        # llvm passes -Werror=date-time which is only supported in gcc-4.9+
         - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
       addons:
         apt:
           sources:
-            - sourceline: 'deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-7 main'
+            - sourceline: 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-7 main'
               key_url: https://apt.llvm.org/llvm-snapshot.gpg.key
             - ubuntu-toolchain-r-test
           packages:
@@ -184,11 +134,12 @@
         - LABEL="cmake gcc LLVM-8"
         - LLVM_VERSION=8
         - CHECK_FILES="barts-r600--.bc cayman-r600--.bc cedar-r600--.bc cypress-r600--.bc tahiti-amdgcn--.bc amdgcn--amdhsa.bc tahiti-amdgcn-mesa-mesa3d.bc nvptx--nvidiacl.bc nvptx64--nvidiacl.bc"
+        # llvm passes -Werror=date-time which is only supported in gcc-4.9+
         - MATRIX_EVAL="CC=gcc-6 && CXX=g++-6"
       addons:
         apt:
           sources:
-            - sourceline: 'deb http://apt.llvm.org/trusty/ llvm-toolchain-trusty-8 main'
+            - sourceline: 'deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-8 main'
               key_url: https://apt.llvm.org/llvm-snapshot.gpg.key
             - ubuntu-toolchain-r-test
           packages: