Merge pull request #79055 from kubamracek/embedded-concurrency-libcxx

[embedded] Prepare the Embedded Concurrency library for building on armv7m/armv7em

Author: kubamracek

stdlib/public/Concurrency/CMakeLists.txt

@@ -247,7 +247,13 @@ if(SWIFT_SHOULD_BUILD_EMBEDDED_STDLIB AND SWIFT_SHOULD_BUILD_EMBEDDED_CONCURRENC
       if(NOT "${mod}" MATCHES "-macos$")
         continue()
       endif()
-      set(extra_c_compile_flags -D__MACH__ -D__APPLE__ -ffreestanding)
+      if("${mod}" MATCHES "riscv")
+        continue()
+      endif()
+      if("${mod}" MATCHES "armv6m")
+        continue()
+      endif()
+      set(extra_c_compile_flags -D__MACH__ -D__APPLE__ -ffreestanding -stdlib=libc++)
       set(extra_swift_compile_flags -Xcc -D__MACH__ -Xcc -D__APPLE__ -Xcc -ffreestanding)
     endif()