Workaround Emscripten CMake issue

-fexceptions causes some issues: emscripten-core/emscripten#18084

After trial and error it seems that moving them to apply only to C++ (via CXXFLAGS) works best.

build.sh

@@ -98,7 +98,7 @@ if [ "$PIC" = "true" ]; then PIC_FLAG=--pic; fi
 #export LDFLAGS+=" --source-map-base http://localhost:3000/lib/"
 
 # Common compiler flags
-export CFLAGS="-O3 -fno-rtti -fexceptions -mnontrapping-fptoint -pthread"
+export CFLAGS="-O3 -fno-rtti -mnontrapping-fptoint -pthread"
 if [ "$SIMD" = "true" ]; then export CFLAGS+=" -msimd128 -DWASM_SIMD_COMPAT_SLOW"; fi
 if [ "$WASM_BIGINT" = "true" ]; then
   # libffi needs to detect WASM_BIGINT support at compile time
@@ -108,7 +108,7 @@ if [ "$WASM_FS" = "true" ]; then export CFLAGS+=" -DWASMFS"; fi
 if [ "$WASM_EH" = "true" ]; then export CFLAGS+=" -sSUPPORT_LONGJMP=wasm"; fi
 if [ "$LTO" = "true" ]; then export CFLAGS+=" -flto"; fi
 if [ "$PIC" = "true" ]; then export CFLAGS+=" -fPIC"; fi
-export CXXFLAGS="$CFLAGS"
+export CXXFLAGS="$CFLAGS -fexceptions"
 export LDFLAGS="-L$TARGET/lib -O3"
 if [ "$WASM_BIGINT" = "true" ]; then export LDFLAGS+=" -sWASM_BIGINT"; fi
 if [ "$WASM_FS" = "true" ]; then export LDFLAGS+=" -sWASMFS"; fi