[wasm] Use response files for emcc invocations

This adds response file for the linker command line, which will be the
longest one. And it uses a known name for the response file.

In future, once we have dependency checking, we can use such response
files for that too.

Fixes #51437 .

src/mono/wasm/build/WasmApp.targets

@@ -486,7 +486,20 @@
 
     <Message Text="Compiling native assets with emcc. This may take a while ..." Importance="High" />
     <Exec Command='emcc $(EmccCFlags) "%(_WasmObjectsToBuild.SourcePath)" -c -o "%(_WasmObjectsToBuild.Identity)"' EnvironmentVariables="@(EmscriptenEnvVars)" />
-    <Exec Command="emcc $(EmccLDFlags) @(_DotnetJSSrcFile->'--js-library &quot;%(Identity)&quot;', ' ') @(_BitcodeFile->'&quot;%(Identity)&quot;', ' ') @(_WasmObjects->'&quot;%(Identity)&quot;', ' ') -o &quot;$(_WasmIntermediateOutputPath)dotnet.js&quot;" EnvironmentVariables="@(EmscriptenEnvVars)" />
+
+    <PropertyGroup>
+      <_EmccLinkerArguments>$(EmccLDFlags)</_EmccLinkerArguments>
+      <_EmccLinkerArguments>$(_EmccLinkerArguments) @(_DotnetJSSrcFile->'--js-library &quot;%(Identity)&quot;', ' ')</_EmccLinkerArguments>
+      <_EmccLinkerArguments>$(_EmccLinkerArguments) @(_BitcodeFile->'&quot;%(Identity)&quot;', ' ')</_EmccLinkerArguments>
+      <_EmccLinkerArguments>$(_EmccLinkerArguments) @(_WasmObjects->'&quot;%(Identity)&quot;', ' ')</_EmccLinkerArguments>
+      <_EmccLinkerArguments>$(_EmccLinkerArguments) -o &quot;$(_WasmIntermediateOutputPath)dotnet.js&quot;</_EmccLinkerArguments>
+
+      <_EmccLinkerResponseFile>$(_WasmIntermediateOutputPath)emcc-link.rsp</_EmccLinkerResponseFile>
+    </PropertyGroup>
+    <WriteLinesToFile Lines="$(_EmccLinkerArguments)" File="$(_EmccLinkerResponseFile)" />
+    <Message Text="Running emcc with $(_EmccLinkerArguments)" Importance="Low" />
+    <Exec Command="emcc @$(_EmccLinkerResponseFile)" EnvironmentVariables="@(EmscriptenEnvVars)" />
+
     <Exec Command='"$(_WasmOptCommand)" --strip-dwarf "$(_WasmIntermediateOutputPath)dotnet.wasm" -o "$(_WasmIntermediateOutputPath)dotnet.wasm"' Condition="'$(WasmNativeStrip)' == 'true'" IgnoreStandardErrorWarningFormat="true" EnvironmentVariables="@(EmscriptenEnvVars)" />
 
     <ItemGroup>