[llvm] On Windows, make the release script work with the local git checkout (PR #78273)

[via llvm-commits]

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@@ -414,14 +423,17 @@ cmake -GNinja %cmake_flags% ^
   -DCMAKE_CXX_COMPILER=%instrumented_clang% ^
   -DLLVM_ENABLE_PROJECTS=clang ^
   -DLLVM_TARGETS_TO_BUILD=Native ^
-  ..\..\llvm-project\llvm || exit /b 1
+  %llvm_src%\llvm || exit /b 1
 REM Drop profiles generated from running cmake; those are not representative.
 del ..\instrument\profiles\*.profraw
 ninja tools/clang/lib/Sema/CMakeFiles/obj.clangSema.dir/Sema.cpp.obj
 cd ..
 set profile=%cd:\=/%/profile.profdata
 %stage0_bin_dir%\llvm-profdata merge -output=%profile% instrument\profiles\*.profraw || exit /b 1
-set cmake_profile_flag=-DLLVM_PROFDATA_FILE=%profile%
+set common_compiler_flags=%common_compiler_flags% -Wno-backend-plugin
+set cmake_profile_flag=-DLLVM_PROFDATA_FILE=%profile% ^
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zmodem wrote:

I suppose it should be `cmake_profile_flags` now that we're passing multiple flags.

https://github.com/llvm/llvm-project/pull/78273