[wasm] Do not use link flags for bitcode compilation (dotnet#101397)

* [wasm] Do not use link flags for bitcode compilation

This avoids errors like:

    /root/helix/work/correlation/build/wasm-shared/WasmApp.Common.targets(832,5): error : emcc: warning: linker setting ignored during compilation: 'EXPORT_ES6' [-Wunused-command-line-argument] [/root/helix/work/workitem/e/publish/ProxyProjectForAOTOnHelix.proj]
    /root/helix/work/correlation/build/wasm-shared/WasmApp.Common.targets(832,5): error : emcc: warning: linker setting ignored during compilation: 'EXPORT_EXCEPTION_HANDLING_HELPERS' [-Wunused-command-line-argument] [/root/helix/work/workitem/e/publish/ProxyProjectForAOTOnHelix.proj]

* Rename _BitcodeLDFlags to _BitcodeCompileFlags

Update the comment as well.

_BitcodeLDFlags were used only for the BC compilation. This way
we keep the possibility to add extra flags via EmccExtraBitcodeCompilationFlags and
WasiClangExtraBitcodeCompileFlags.

src/mono/browser/build/BrowserWasmApp.targets

@@ -406,8 +406,8 @@
 
   <Target Name="_BrowserWasmBeforeWriteCompileBitcodeRsp" BeforeTargets="_WasmWriteRspForCompilingBitcode">
     <ItemGroup>
-      <_BitcodeLDFlags Include="@(_EmccLDFlags)" />
-      <_BitcodeLDFlags Include="$(EmccExtraBitcodeLDFlags)" />
+      <_BitcodeCompileFlags Include="@(_EmccCommonFlags)" />
+      <_BitcodeCompileFlags Include="$(EmccExtraBitcodeCompilationFlags)" />
     </ItemGroup>
   </Target>
 

src/mono/wasi/build/WasiApp.targets

@@ -265,8 +265,8 @@
   <!-- FIXME: merge with some other target -->
   <Target Name="_WasiBeforeWriteRspForCompilingBitcodeRsp" BeforeTargets="_WasmWriteRspForCompilingBitcode">
     <ItemGroup>
-      <_BitcodeLDFlags Include="@(_WasiClangLDFlags)" />
-      <_BitcodeLDFlags Include="$(WasiClangExtraBitcodeLDFlags)" />
+      <_BitcodeCompileFlags Include="@(_WasiClangCommonFlags)" />
+      <_BitcodeCompileFlags Include="$(WasiClangExtraBitcodeCompileFlags)" />
     </ItemGroup>
   </Target>
 

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

@@ -800,11 +800,11 @@
   <Target Name="_WasmSelectRuntimeComponentsForLinking" Condition="'$(WasmIsWorkloadAvailable)' == 'true'" DependsOnTargets="_MonoSelectRuntimeComponents" />
 
   <!--
-    Inputs: @(_BitcodeLDFlags), $(_WasmCompileBitcodeRsp)
+    Inputs: @(_BitcodeCompileFlags), $(_WasmCompileBitcodeRsp)
     Outputs: file @(_WasmCompileBitcodeRsp
   -->
   <Target Name="_WasmWriteRspForCompilingBitcode">
-    <WriteLinesToFile Lines="@(_BitcodeLDFlags)" File="$(_WasmCompileBitcodeRsp)" Overwrite="true" WriteOnlyWhenDifferent="true" />
+    <WriteLinesToFile Lines="@(_BitcodeCompileFlags)" File="$(_WasmCompileBitcodeRsp)" Overwrite="true" WriteOnlyWhenDifferent="true" />
     <ItemGroup>
       <FileWrites Include="$(_WasmCompileBitcodeRsp)" />
     </ItemGroup>