Set CMAKE_CXX_FLAGS_RELEASE only for non-MSVC compilers

Author: kubamracek

CMakeLists.txt

@@ -629,14 +629,17 @@ if("${CMAKE_C_COMPILER_ID}" STREQUAL "MSVC" OR "${CMAKE_CXX_SIMULATE_ID}" STREQU
   set(SWIFT_COMPILER_IS_MSVC_LIKE TRUE)
 endif()
 
-# Avoid CMake's default -O3 for Release builds.
-set(CMAKE_CXX_FLAGS_RELEASE "-O2 -DNDEBUG")
 if(NOT SWIFT_COMPILER_IS_MSVC_LIKE)
+  # Avoid CMake's default -O3 for Release builds.
+  set(CMAKE_CXX_FLAGS_RELEASE "-O2 -DNDEBUG")
+
   _compute_lto_flag("${SWIFT_TOOLS_ENABLE_LTO}" _lto_flag_out)
   if(_lto_flag_out)
     set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_RELEASE} -gline-tables-only")
     set(CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -gline-tables-only")
   endif()
+else()
+  
 endif()
 
 #