[llvm] [openmp] Remaining work necessary for GCC 15 (PR #157385)

[via llvm-commits]

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@@ -195,6 +195,14 @@ function (add_flangrt_library name)
       # Use same stem name for .a and .so. Common in UNIX environments.
       # Not possible in Windows environments.
       set_target_properties(${tgtname} PROPERTIES OUTPUT_NAME "${name}")
+
+      # Must use minimum optimization level of -O2 to prevent dependency on libstdc++
+      string(REPLACE "-O0" "-O2" CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS)
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jprotze wrote:

Why first replace and then passing -O2 to the private flags anyways?

https://github.com/llvm/llvm-project/pull/157385