Add BUILD_NATIVE flag. Closes #130

CMakeLists.txt

@@ -3,6 +3,8 @@ cmake_minimum_required(VERSION 3.11)
 set(BUILD_WASI "uvwasi" CACHE STRING "WASI implementation")
 set_property(CACHE BUILD_WASI PROPERTY STRINGS none simple uvwasi metawasi)
 
+set(BUILD_NATIVE "Build with machine-specific optimisations" ON)
+
 set(OUT_FILE "wasm3")
 set(APP_DIR  "platforms/app")
 
@@ -153,7 +155,12 @@ else()
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Werror=shadow")
   endif()
 
-  set(CMAKE_C_FLAGS_RELEASE "-O3 -march=native -Wfatal-errors -fomit-frame-pointer -fno-stack-check -fno-stack-protector") #-fno-inline
+  set(CMAKE_C_FLAGS_RELEASE "-O3 -Wfatal-errors -fomit-frame-pointer -fno-stack-check -fno-stack-protector") #-fno-inline
+
+  if(BUILD_NATIVE)
+    set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -march=native")
+  endif()
+
   set(CMAKE_EXE_LINKER_FLAGS_DEBUG "-O0")
   set(CMAKE_EXE_LINKER_FLAGS_RELEASE "-O3")