[clang] [Fuchsia] Explicitly set C++ standard C++23 in libcxx tests (PR #73760)

[Petr Hosek via cfe-commits]

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@@ -136,6 +136,7 @@ if(WIN32 OR LLVM_WINSYSROOT)
   set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS ${WINDOWS_LINK_FLAGS} CACHE STRING "")
   set(RUNTIMES_${target}_CMAKE_SHARED_LINKER_FLAGS ${WINDOWS_LINK_FLAGS} CACHE STRING "")
   set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS ${WINDOWS_LINK_FLAGS} CACHE STRING "")
+  set(RUNTIMES_${target}_LIBCXX_TEST_PARAMS "std=c++23" CACHE STRING "")
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petrhosek wrote:

This is just a nit, but can you move this next to the other `*_LIBCXX_*` flags in this block?

https://github.com/llvm/llvm-project/pull/73760