[zorg][PowerPC] Switch RHEL buildbot to use runtime build

We are using runtime build now,
See Petr's definition about "runtime" build here:
http://lists.llvm.org/pipermail/llvm-dev/2020-April/140771.html

Update the cmake macros to reflect the change.

Reviewed By: saghir

Differential Revision: https://reviews.llvm.org/D90609
diff --git a/buildbot/osuosl/master/config/builders.py b/buildbot/osuosl/master/config/builders.py
index 1ba6b78..d6b49fb 100644
--- a/buildbot/osuosl/master/config/builders.py
+++ b/buildbot/osuosl/master/config/builders.py
@@ -593,6 +593,8 @@
                     stage1_config='Release',
                     nt_flags=['--threads=16', '--build-threads=16'],
                     extra_cmake_args=[
+                        '-DLLVM_ENABLE_PROJECTS=clang;llvm;clang-tools-extra;lld',
+                        '-DLLVM_ENABLE_RUNTIMES=compiler-rt',
                         "-DLLVM_ENABLE_ASSERTIONS=On", "-DCMAKE_C_COMPILER=clang",
                         "-DCMAKE_CXX_COMPILER=clang++",
                         "-DCLANG_DEFAULT_LINKER=lld",