Disable use of Clang flag -fswift-async-fp=

Author: DougGregor

stdlib/public/Concurrency/CMakeLists.txt

@@ -41,13 +41,10 @@ endif()
 # Don't emit extended frame info on platforms other than darwin, system
 # backtracer and system debugger are unlikely to support it.
 if(CMAKE_SYSTEM_NAME STREQUAL Darwin)
-  list(APPEND SWIFT_RUNTIME_CONCURRENCY_C_FLAGS
-    "-fswift-async-fp=${swift_concurrency_async_fp_mode}")
   list(APPEND SWIFT_RUNTIME_CONCURRENCY_SWIFT_FLAGS
     "-Xfrontend"
     "-swift-async-frame-pointer=${swift_concurrency_async_fp_mode}")
 else()
-  list(APPEND SWIFT_RUNTIME_CONCURRENCY_C_FLAGS "-fswift-async-fp=never")
 endif()
 
 add_swift_target_library(swift_Concurrency ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB