[wasm] Allow to build browser in library mode (#106388)

Author: mkhamoyan

src/mono/browser/build/BrowserWasmApp.targets

@@ -63,6 +63,15 @@
     <ProjectCapability Include="DotNetCoreWeb"/>
   </ItemGroup>
 
+  <!-- When trimming non-exe projects, root the whole intermediate assembly. -->
+  <Target Name="_RootEntireIntermediateAssembly" AfterTargets="PrepareForILLink" BeforeTargets="_RunILLink" Condition="'$(RuntimeIdentifier)' == 'browser-wasm' And '$(OutputType)' == 'Library'">
+    <ItemGroup>
+      <TrimmerRootAssembly Condition="'%(Identity)' == '@(IntermediateAssembly)'">
+        <RootMode>all</RootMode>
+      </TrimmerRootAssembly>
+    </ItemGroup>
+  </Target>
+
   <Target Name="_GetWasmGenerateAppBundleDependencies">
     <Warning Condition="'$(InvariantGlobalization)' == 'true' and '$(HybridGlobalization)' == 'true'" Text="%24(HybridGlobalization) has no effect when %24(InvariantGlobalization) is set to true." />
     <Warning Condition="'$(WasmIcuDataFileName)' != '' and '$(HybridGlobalization)' == 'true'" Text="%24(WasmIcuDataFileName) has no effect when %24(HybridGlobalization) is set to true." />

src/mono/browser/runtime/driver.c

@@ -180,9 +180,12 @@ cleanup_runtime_config (MonovmRuntimeConfigArguments *args, void *user_data)
 	free (user_data);
 }
 
+static int runtime_initialized = 0;
+
 EMSCRIPTEN_KEEPALIVE void
 mono_wasm_load_runtime (int debug_level)
 {
+	runtime_initialized = 1;
 	const char *interp_opts = "";
 
 #ifndef INVARIANT_GLOBALIZATION
@@ -227,6 +230,15 @@ mono_wasm_load_runtime (int debug_level)
 	bindings_initialize_internals();
 }
 
+int initialize_runtime()
+{
+    if (runtime_initialized == 1)
+		return 0;
+	mono_wasm_load_runtime (0);
+
+	return 0;
+}
+
 EMSCRIPTEN_KEEPALIVE void
 mono_wasm_invoke_jsexport (MonoMethod *method, void* args)
 {