[libcxx] i think it is CMAKE_CXX_COMPILER_FRONT_VARIANT, not CMAKE_CXX_SIMULATE_ID

https://github.com/ldionne/llvm-project/blob/acb3d81a932c094ee1e71bca6aa60e69cac43c65/libcxx/CMakeLists.txt#L38
I got this failure
```
/home/mhcenlskehg/toolchains/llvm/x86_64-linux-gnu/llvm/bin/clang++ --target=x86_64-unknown-windows-msvc -DLIBC_NAMESPACE=__llvm_libc_common_utils -D_ALLOW_ITERATOR_DEBUG_LEVEL_MISMATCH -D_ALLOW_MSC_VER_MISMATCH -D_CRTBLD -D_CRT_SECURE_NO_WARNINGS -D_CRT_STDIO_ISO_WIDE_SPECIFIERS -D_LIBCPP_AVAILABILITY_MINIMUM_HEADER_VERSION=2 -D_LIBCPP_BUILDING_LIBRARY -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/mhcenlskehg/toolchains_build/llvm-project/libcxx/src -I/home/mhcenlskehg/toolchains_build/toolchainbuildscripts/llvm/.llvmwindowsmsvclibcxxartifacts/x86_64-unknown-windows-msvc/runtimes/include/c++/v1 -I/home/mhcenlskehg/toolchains_build/llvm-project/cmake/Modules/../../libc -fuse-ld=lld -flto=thin -D_DLL=1 -stdlib=libc++ -Wno-unused-command-line-argument -lmsvcrt -lmsvcprt --sysroot=/home/mhcenlskehg/toolchains/windows-msvc-sysroot -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -ffunction-sections -fdata-sections -Xclang -fno-pch-timestamp -O3 -DNDEBUG -std=gnu++17 -D_DLL -D_MT -Xclang --dependent-lib=msvcrt /std:c++latest -faligned-allocation -nostdinc++ -fvisibility-inlines-hidden -fvisibility=hidden -fsized-deallocation -Wall -Wextra -Wnewline-eof -Wshadow -Wwrite-strings -Wno-unused-parameter -Wno-long-long -Werror=return-type -Wextra-semi -Wundef -Wunused-template -Wformat-nonliteral -Wzero-length-array -Wdeprecated-redundant-constexpr-static-def -Wno-nullability-completeness -Wmissing-prototypes -Wno-user-defined-literals -Wno-covered-switch-default -Wno-suggest-override -Wno-c++98-compat -Wno-c++98-compat-pedantic -Wno-c++11-compat -Wno-undef -Wno-reserved-id-macro -Wno-gnu-include-next -Wno-gcc-compat -Wno-zero-as-null-pointer-constant -Wno-deprecated-dynamic-exception-spec -Wno-sign-conversion -Wno-old-style-cast -Wno-deprecated -Wno-shift-sign-overflow -Wno-double-promotion -Wno-error -fdebug-prefix-map=/home/mhcenlskehg/toolchains_build/toolchainbuildscripts/llvm/.llvmwindowsmsvclibcxxartifacts/x86_64-unknown-windows-msvc/runtimes/include/c++/v1=/home/mhcenlskehg/toolchains_build/llvm-project/libcxx/include -MD -MT libcxx/src/CMakeFiles/cxx_shared.dir/filesystem/path.cpp.obj -MF libcxx/src/CMakeFiles/cxx_shared.dir/filesystem/path.cpp.obj.d -o libcxx/src/CMakeFiles/cxx_shared.dir/filesystem/path.cpp.obj -c /home/mhcenlskehg/toolchains_build/llvm-project/libcxx/src/filesystem/path.cpp
clang++: error: no such file or directory: '/std:c++latest'
```

Inspect libcxx/CMakeLists.txt around line 38, focusing on how CMAKE_CXX_SIMULATE_ID and CMAKE_CXX_COMPILER_FRONT_VARIANT are used. Reproduce the reported clang++ build targeting Windows MSVC and verify that the generated compile command no longer treats /std:c++latest as an invalid file path.

Written by the indexing model from the issue text.