Add build flag to disable build of libwasm (#1435)

This allows the wabt tools to be build with no git submodules

Author: dschuff

CMakeLists.txt

@@ -39,6 +39,7 @@ endif ()
 option(BUILD_TESTS "Build GTest-based tests" ON)
 option(USE_SYSTEM_GTEST "Use system GTest, instead of building" OFF)
 option(BUILD_TOOLS "Build wabt commandline tools" ON)
+option(BUILD_LIBWASM "Build libwasm" ON)
 option(USE_ASAN "Use address sanitizer" OFF)
 option(USE_MSAN "Use memory sanitizer" OFF)
 option(USE_LSAN "Use leak sanitizer" OFF)
@@ -328,16 +329,18 @@ set(WABT_LIBRARY_SRC
 add_library(wabt STATIC ${WABT_LIBRARY_SRC})
 
 # libwasm, which implenents the wasm C API
-add_library(wasm SHARED ${WABT_LIBRARY_SRC} src/interp/interp-wasm-c-api.cc)
-target_link_libraries(wasm wabt)
-target_include_directories(wasm PUBLIC third_party/wasm-c-api/include)
-if (COMPILER_IS_MSVC)
-  target_compile_definitions(wasm PRIVATE "WASM_API_EXTERN=__declspec(dllexport)")
-else ()
-  target_compile_options(wasm PRIVATE -Wno-old-style-cast)
-  target_compile_definitions(wasm PRIVATE "WASM_API_EXTERN=__attribute__((visibility(\"default\")))")
+if (BUILD_LIBWASM)
+  add_library(wasm SHARED ${WABT_LIBRARY_SRC} src/interp/interp-wasm-c-api.cc)
+  target_link_libraries(wasm wabt)
+  target_include_directories(wasm PUBLIC third_party/wasm-c-api/include)
+  if (COMPILER_IS_MSVC)
+    target_compile_definitions(wasm PRIVATE "WASM_API_EXTERN=__declspec(dllexport)")
+  else ()
+    target_compile_options(wasm PRIVATE -Wno-old-style-cast)
+    target_compile_definitions(wasm PRIVATE "WASM_API_EXTERN=__attribute__((visibility(\"default\")))")
+  endif ()
+  set_target_properties(wasm PROPERTIES CXX_VISIBILITY_PRESET hidden)
 endif ()
-set_target_properties(wasm PROPERTIES CXX_VISIBILITY_PRESET hidden)
 
 if (NOT EMSCRIPTEN)
   if (CODE_COVERAGE)