CMake: remove clang workaround

Author: andreasbuhr

cmake/FindCppcoroCoroutines.cmake

@@ -15,21 +15,6 @@ if(Coroutines_SUPPORTS_MS_FLAG)
 elseif(Coroutines_ts_SUPPORTS_GNU_FLAG)
     check_include_file_cxx("coroutine" Coroutines_STANDARD_LIBRARY_SUPPORT "-fcoroutines-ts")
     check_include_file_cxx("experimental/coroutine" Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT "-fcoroutines-ts")
-    # workaround:
-    #  clang not find stdlibc++ headers when on ubuntu 20.04
-    #  So, we retry with libc++ enforcement
-    if(NOT Coroutines_STANDARD_LIBRARY_SUPPORT
-      AND NOT Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT
-      AND CMAKE_CXX_COMPILER_ID MATCHES Clang)
-        set(CMAKE_REQUIRED_FLAGS "-stdlib=libc++")
-        check_include_file_cxx("coroutine" Coroutines_STANDARD_LIBRARY_SUPPORT_LIBCPP "-fcoroutines-ts")
-        check_include_file_cxx("experimental/coroutine" Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT_LIBCPP "-fcoroutines-ts")
-        if(Coroutines_STANDARD_LIBRARY_SUPPORT_LIBCPP OR Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT_LIBCPP)
-          list(APPEND Coroutines_EXTRA_FLAGS "-stdlib=libc++")
-          set(Coroutines_STANDARD_LIBRARY_SUPPORT ${Coroutines_STANDARD_LIBRARY_SUPPORT_LIBCPP})
-          set(Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT ${Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT_LIBCPP})
-        endif()
-    endif()
 elseif(Coroutines_SUPPORTS_GNU_FLAG)
     check_include_file_cxx("coroutine" Coroutines_STANDARD_LIBRARY_SUPPORT "-fcoroutines")
     check_include_file_cxx("experimental/coroutine" Coroutines_EXPERIMENTAL_LIBRARY_SUPPORT "-fcoroutines")