Embedded Synchronization: enable Mutex for Wasm

We have both WASI-libc and pthread available for Wasm, which should be enough for making this type available.

Author: MaxDesiatov

stdlib/public/Synchronization/CMakeLists.txt

@@ -192,13 +192,24 @@ if(SWIFT_SHOULD_BUILD_EMBEDDED_STDLIB)
     if(SWIFT_EMBEDDED_STDLIB_SDKS_FOR_TARGET_TRIPLES)
       set(SWIFT_SDK_embedded_ARCH_${arch}_PATH "${EMBEDDED_STDLIB_SDK_FOR_${triple}}")
     endif()
+
+    set(SWIFT_SYNCHRONIZATION_EMBEDDED_SOURCES)
+    list(APPEND SWIFT_SYNCHRONIZATION_EMBEDDED_SOURCES ${SWIFT_SYNCHRONIZATION_ATOMIC_SOURCES})
+
+    if("${arch}" MATCHES "wasm32")
+      list(APPEND SWIFT_SYNCHRONIZATION_EMBEDDED_SOURCES
+        ${SWIFT_SYNCHRONIZATION_WASM_SOURCES}
+      )
+    endif()
+      
     add_swift_target_library_single(
       embedded-synchronization-${mod}
       swiftSynchronization
       ONLY_SWIFTMODULE
       IS_FRAGILE
 
-      ${SWIFT_SYNCHRONIZATION_ATOMIC_SOURCES}
+      ${SWIFT_SYNCHRONIZATION_EMBEDDED_SOURCES}
+      
       GYB_SOURCES
         ${SWIFT_SYNCHRONIZATION_GYB_SOURCES}