[mono][wasm] Avoid compiling llvm bitcode files with -emit-llvm.

It causes the output to be a bitcode file as well, which is
passed to the emscripten link step, which will compile it
to wasm sequentially, slowing down linking.

Fixes dotnet#54935.

src/mono/wasm/build/WasmApp.Native.targets

@@ -218,6 +218,7 @@
       <_EmccCFlags Include="-DLINK_ICALLS=1"                   Condition="'$(WasmLinkIcalls)' == 'true'" />
       <_EmccCFlags Include="-DCORE_BINDINGS" />
       <_EmccCFlags Include="-DGEN_PINVOKE=1" />
+      <_EmccCFlags Include="-emit-llvm" />
 
       <_EmccCFlags Include="&quot;-I%(_EmccIncludePaths.Identity)&quot;" />
       <_EmccCFlags Include="-g" Condition="'$(WasmNativeDebugSymbols)' == 'true'" />

src/mono/wasm/wasm.proj

@@ -69,7 +69,6 @@
       <_EmccCommonFlags Include="-s &quot;EXPORTED_RUNTIME_METHODS=['ccall', 'FS_createPath', 'FS_createDataFile', 'cwrap', 'setValue', 'getValue', 'UTF8ToString', 'UTF8ArrayToString', 'addFunction']&quot;" />
       <_EmccCommonFlags Include="-s &quot;EXPORTED_FUNCTIONS=['_putchar']&quot;" />
       <_EmccCommonFlags Include="--source-map-base http://example.com" />
-      <_EmccCommonFlags Include="-emit-llvm" />
 
       <_EmccCommonFlags Include="-s MODULARIZE=1" Condition="'$(WasmEnableES6)' != 'false'" />
       <_EmccCommonFlags Include="-s EXPORT_ES6=1" Condition="'$(WasmEnableES6)' != 'false'" />