[wasm] Explicitly include mscorlib.dll, to support scanning assemblies (#69886)

* [wasm] Explicitly include mscorlib.dll, to support scanning assemblies

.. with mscorlib dependency.

This showed up when scanning `Dia2Lib` for icalls, which is indirectly
used by the microbenchmarks in `dotnet/performance`. It would fail with:

```
System.IO.FileNotFoundException: Could not find assembly 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'.
Either explicitly load this assembly using a method such as LoadFromAssemblyPath() or use a MetadataAssemblyResolver that returns a valid assembly.
   at System.Reflection.TypeLoading.Ecma.EcmaResolver.ResolveAssembly(AssemblyReferenceHandle handle, EcmaModule module)
   at System.Reflection.TypeLoading.Ecma.EcmaResolver.ComputeTypeRefResolution(TypeReferenceHandle handle, EcmaModule module)
   at System.Reflection.TypeLoading.Ecma.EcmaResolver.ResolveTypeRef(TypeReferenceHandle handle, EcmaModule module)
   at System.Reflection.TypeLoading.Ecma.EcmaModule.GetTypeFromReference(MetadataReader reader, TypeReferenceHandle handle, Byte rawTypeKind)
   at System.Reflection.Metadata.Ecma335.SignatureDecoder`2.DecodeTypeHandle(BlobReader& blobReader, Byte rawTypeKind, Boolean allowTypeSpecifications)
   at System.Reflection.Metadata.Ecma335.SignatureDecoder`2.DecodeType(BlobReader& blobReader, Boolean allowTypeSpecifications, Int32 typeCode)
   at System.Reflection.Metadata.Ecma335.SignatureDecoder`2.DecodeType(BlobReader& blobReader, Boolean allowTypeSpecifications, Int32 typeCode)
   at System.Reflection.Metadata.Ecma335.SignatureDecoder`2.DecodeMethodSignature(BlobReader& blobReader)
   at System.Reflection.TypeLoading.Ecma.EcmaMethodDecoder.SpecializeMethodSig(IRoMethodBase roMethodBase)
   at System.Reflection.TypeLoading.RoDefinitionMethod`1.ComputeMethodSig()
   at System.Reflection.TypeLoading.RoMethod.get_ReturnType()
   at SignatureMapper.MethodToSignature(MethodInfo method)
   at IcallTableGenerator.<ProcessType>g__AddSignature|15_1(Type type, MethodInfo method)
   at IcallTableGenerator.ProcessType(Type type)
   at IcallTableGenerator.GenIcallTable(String runtimeIcallTableFile, String[] assemblies, String outputPath)
   at ManagedToNativeGenerator.ExecuteInternal()
   at ManagedToNativeGenerator.Execute()
   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
   at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask)
```

This is thrown when `SignatureMapper.MethodToSignature` called
`method.ReturnType` for:

```
  .method public hidebysig newslot virtual
  instance void  loadAndValidateDataFromPdb([in] string  marshal( lpwstr) pdbPath,
                                            [in] [mscorlib]System.Guid& pcsig70,
                                            [in] uint32 sig,
                                            [in] uint32 age) runtime managed internalcall
  {
    .override Dia2Lib.IDiaDataSource::loadAndValidateDataFromPdb
  } // end of method DiaSourceClass::loadAndValidateDataFromPdb
```

We use `PathAssemblyResolver` with a closed set of assemblies, which
didn't include mscorlib.dll . So, we include that explicitly from the
runtime pack.

Fixes https://github.com/dotnet/runtime/issues/69861

* Add mscorlib.dll, only if it wasn't already there.

`System.Reflection.MetadataLoadContext.Tests` tests failed:

```
The "ManagedToNativeGenerator" task failed unexpectedly. [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
System.IO.FileLoadException: The assembly 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' has already loaded been loaded into this MetadataLoadContext. [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at System.Reflection.MetadataLoadContext.LoadFromStreamCore(Stream peStream) [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at System.Reflection.MetadataLoadContext.LoadFromAssemblyPath(String assemblyPath) [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at PInvokeTableGenerator.GenPInvokeTable(String[] pinvokeModules, String[] assemblies, String outputPath) in /_/src/tasks/WasmAppBuilder/PInvokeTableGenerator.cs:line 37 [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at ManagedToNativeGenerator.ExecuteInternal() in /_/src/tasks/WasmAppBuilder/ManagedToNativeGenerator.cs:line 71 [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at ManagedToNativeGenerator.Execute() in /_/src/tasks/WasmAppBuilder/ManagedToNativeGenerator.cs:line 56 [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [/datadisks/disk1/work/9ABB086E/w/BDA50A35/e/publish/ProxyProjectForAOTOnHelix.proj]
   at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask)
```

1 files changed, 7 insertions, 2 deletions

diff --git a/src/mono/wasm/build/WasmApp.Native.targets b/src/mono/wasm/build/WasmApp.Native.targets
index 317597e45db..2a700da6487 100644
--- a/src/mono/wasm/build/WasmApp.Native.targets
+++ b/src/mono/wasm/build/WasmApp.Native.targets
@@ -272,7 +272,12 @@
       <_WasmPInvokeModules Include="libSystem.Globalization.Native" />
       <_WasmPInvokeModules Include="libSystem.Security.Cryptography.Native.Browser" />
     </ItemGroup>
-    
+
+    <PropertyGroup>
+      <_HasMscorlib Condition="'%(_WasmAssembliesInternal.FileName)%(_WasmAssembliesInternal.Extension)' == 'mscorlib.dll'">true</_HasMscorlib>
+      <_MscorlibPath Condition="'$(_HasMscorlib)' != 'true'">$(MicrosoftNetCoreAppRuntimePackRidDir)lib\net7.0\mscorlib.dll</_MscorlibPath>
+    </PropertyGroup>
+
     <Error Condition="'$(_MonoAotCrossCompilerPath)' == '' or !Exists('$(_MonoAotCrossCompilerPath)')"
            Text="Could not find AOT cross compiler at %24(_MonoAotCrossCompilerPath)=$(_MonoAotCrossCompilerPath)" />
 
@@ -284,7 +289,7 @@
     <MakeDir Directories="$(_WasmIntermediateOutputPath)" Condition="!Exists('$(_WasmIntermediateOutputPath)')"  />
 
     <ManagedToNativeGenerator
-      Assemblies="@(_WasmAssembliesInternal)"
+      Assemblies="@(_WasmAssembliesInternal);$(_MscorlibPath)"
       RuntimeIcallTableFile="$(_WasmRuntimeICallTablePath)"
       IcallOutputPath="$(_WasmICallTablePath)"
       PInvokeModules="@(_WasmPInvokeModules)"