[llvm-cov] NFC: Specify a specific C++ standard in the test.

Makes life easier for downstream users with customized default standard.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@372674 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/profile/instrprof-merging.cpp b/test/profile/instrprof-merging.cpp
index 06f05ce..692b049 100644
--- a/test/profile/instrprof-merging.cpp
+++ b/test/profile/instrprof-merging.cpp
@@ -1,8 +1,11 @@
 // 1) Compile shared code into different object files and into an executable.
 
-// RUN: %clangxx_profgen -fcoverage-mapping %s -c -o %t.v1.o -D_VERSION_1
-// RUN: %clangxx_profgen -fcoverage-mapping %s -c -o %t.v2.o -D_VERSION_2
-// RUN: %clangxx_profgen -fcoverage-mapping %t.v1.o %t.v2.o -o %t.exe
+// RUN: %clangxx_profgen -std=c++14 -fcoverage-mapping %s -c -o %t.v1.o \
+// RUN:                  -D_VERSION_1
+// RUN: %clangxx_profgen -std=c++14 -fcoverage-mapping %s -c -o %t.v2.o \
+// RUN:                  -D_VERSION_2
+// RUN: %clangxx_profgen -std=c++14 -fcoverage-mapping %t.v1.o %t.v2.o \
+// RUN:                  -o %t.exe
 
 // 2) Collect profile data.