[clang] [Clang][CMake] Support perf, LBR, and Instrument CLANG_BOLT options (PR #69133)

[David Spickett via cfe-commits]

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@@ -850,23 +850,38 @@ if (CLANG_ENABLE_BOOTSTRAP)
   endforeach()
 endif()
 
-if (CLANG_BOLT_INSTRUMENT AND NOT LLVM_BUILD_INSTRUMENTED)
+set(CLANG_BOLT "INSTRUMENT" CACHE STRING "Apply BOLT optimization to Clang. \
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DavidSpickett wrote:

Wild guess, this defaults to `INSTRUMENT`, but it should default to some `OFF` value?

https://github.com/llvm/llvm-project/pull/69133