fix gcc build

Author: yamt

lib/CMakeLists.txt

@@ -136,7 +136,9 @@ endif()
 endif()
 
 # random things to experiment
+if(CMAKE_C_COMPILER_ID MATCHES "Clang")
 target_compile_options(toywasm-lib-core PUBLIC "SHELL:-Xclang -fmerge-functions" "SHELL:-mllvm -mergefunc-use-aliases")
+endif()
 #target_compile_options(toywasm-lib-core PUBLIC "SHELL:-mllvm -enable-machine-outliner")
 #target_compile_options(toywasm-lib-core PUBLIC "SHELL:-mllvm -hot-cold-split")
 #target_compile_options(toywasm-lib-core PUBLIC "SHELL:-mllvm --enable-gvn-hoist")