[clang] [clang][perf-training] Support excluding LLVM build from PGO training (PR #126876)

[Tom Stellard via cfe-commits]

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@@ -11,6 +11,7 @@ config.python_exe = "@Python3_EXECUTABLE@"
 config.cmake_exe = "@CMAKE_COMMAND@"
 config.llvm_src_dir ="@CMAKE_SOURCE_DIR@"
 config.cmake_generator ="@CMAKE_GENERATOR@"
+config.use_llvm_build = @CLANG_PGO_TRAINING_USE_LLVM_BUILD@
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tstellar wrote:

`@CLANG_PGO_TRAINING_USE_LLVM_BUILD@` needs to be quoted.  This is causing  a build failure in the Release build configuration.

https://github.com/llvm/llvm-project/pull/126876