build: reset LLVM warning flags

LLVM unfortunately defines global compile flags that are inherited by all other targets in the project, including fetched dependencies. Warning flags, with are functionally unnecessary, can cause conflicts with other targets.

fix #251

CMakeLists.txt

@@ -84,6 +84,8 @@ list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
 include(HandleLLVMOptions)
 add_definitions(${LLVM_DEFINITIONS})
 llvm_map_components_to_libnames(llvm_libs all)
+string(REGEX REPLACE " /W[0-4]" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+string(REGEX REPLACE " /W[0-4]" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 
 # Duktape
 if(NOT DEFINED DUKTAPE_SOURCE_ROOT)