Add core/threadasm.S to druntime.

This is required for PPC and MIPS targets. Results in an empty
object file on other CPU architectures.

CMakeLists.txt

@@ -70,7 +70,9 @@ file(MAKE_DIRECTORY
     ${PROJECT_BINARY_DIR}/${DMDFE_PATH}
 )
 
-if(MSVC)
+if(UNIX)
+    ENABLE_LANGUAGE(ASM)
+elseif(MSVC)
     ENABLE_LANGUAGE(ASM_MASM)
 endif()
 

runtime/CMakeLists.txt

@@ -95,6 +95,7 @@ file(GLOB_RECURSE CORE_D_WIN ${RUNTIME_DIR}/src/core/sys/windows/*.d)
 set(CORE_D_SYS)
 if(UNIX)
     list(APPEND CORE_D_SYS ${CORE_D_UNIX})
+    list(APPEND DCRT_C ${RUNTIME_DIR}/src/core/threadasm.S)
     if(APPLE)
         list(APPEND CORE_D_SYS ${CORE_D_OSX})
     endif()