[llvm] [Support] Vendor rpmalloc in-tree and use it for the Windows 64-bit release (PR #91862)

[Alexandre Ganea via llvm-commits]

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@@ -163,6 +163,8 @@ set common_cmake_flags=^
   -DCLANG_ENABLE_LIBXML2=OFF ^
   -DCMAKE_C_FLAGS="%common_compiler_flags%" ^
   -DCMAKE_CXX_FLAGS="%common_compiler_flags%" ^
+  -DLLVM_ENABLE_RPMALLOC=ON ^
+  -DLLVM_ENABLE_PDB=ON ^
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aganea wrote:

Removed, I had it for debugging. Will propose that separately.

https://github.com/llvm/llvm-project/pull/91862