[compiler-rt][CMake] Fix build when specifying --stdlib= (with 2 dashes) (#136111)

You can pass the stdlib argument either as -stdlib and --stdlib - the
previous regex did not account for this however - which caused the build
to fail, as a --stdlib argument would be replaced with a single dash,
causing clang to assume reading from stdin and the build to fail:

clang++: error: -E or -x required when input is from standard input
clang++: error: cannot specify -o when generating multiple output files

The files
[libcxxabi/CMakeLists.txt](bf6986f9f0/libcxxabi/CMakeLists.txt (L261))
and
[libunwind/CMakeLists.txt](bf6986f9f0/libunwind/CMakeLists.txt (L257))
account for this by removing --stdlib first.

Co-authored-by: Vitaly Buka <vitalybuka@google.com>

compiler-rt/CMakeLists.txt

@@ -607,8 +607,8 @@ append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ SANITIZER_COMMON_CFLA
 append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SANITIZER_COMMON_LINK_FLAGS)
 
 # Remove -stdlib= which is unused when passing -nostdinc++...
-string(REGEX MATCHALL "-stdlib=[a-zA-Z+]*" stdlib_flag "${CMAKE_CXX_FLAGS}")
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX MATCHALL "-?-stdlib=[a-zA-Z+]*" stdlib_flag "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-?-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # ...we need it to build some runtimes and tests so readd it where appropriate.
 list(APPEND COMPILER_RT_COMMON_CFLAGS ${stdlib_flag})

compiler-rt/lib/gwp_asan/CMakeLists.txt

@@ -39,7 +39,7 @@ append_list_if(COMPILER_RT_HAS_FPIC_FLAG -fPIC GWP_ASAN_CFLAGS)
 # append_list_if(COMPILER_RT_HAS_SANITIZER_COMMON ${SANITIZER_COMMON_CFLAGS} GWP_ASAN_CFLAGS)
 
 # Remove -stdlib= which is unused when passing -nostdinc++.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-?-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # Options parsing support is optional. This is an optional library that can be
 # used by an allocator to automatically parse GwpAsan options from the

compiler-rt/lib/msan/tests/CMakeLists.txt

@@ -46,7 +46,7 @@ set(MSAN_UNITTEST_COMMON_CFLAGS
   -fno-sanitize-memory-param-retval  # unittests test mostly this mode.
 )
 # Remove -stdlib= which is unused when passing -nostdinc++.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
+string(REGEX REPLACE "-?-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})
 
 set(MSAN_UNITTEST_INSTRUMENTED_CFLAGS
   ${MSAN_UNITTEST_COMMON_CFLAGS}

compiler-rt/lib/profile/CMakeLists.txt

@@ -163,7 +163,7 @@ endif()
 # We don't use the C++ Standard Library here, so avoid including it by mistake.
 append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ EXTRA_FLAGS)
 # XRay uses C++ standard library headers.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-?-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # This appears to be a C-only warning banning the use of locals in aggregate
 # initializers. All other compilers accept this, though.

compiler-rt/lib/scudo/standalone/CMakeLists.txt

@@ -13,7 +13,7 @@ list(APPEND SCUDO_CFLAGS
   -nostdinc++)
 
 # Remove -stdlib= which is unused when passing -nostdinc++.
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+string(REGEX REPLACE "-?-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 append_list_if(COMPILER_RT_HAS_FVISIBILITY_HIDDEN_FLAG -fvisibility=hidden SCUDO_CFLAGS)