Build integration support for Bionic in NativeAOT (dotnet#87595)

Doesn't actually work E2E because the inline threadstatics work broke our Android support (the one added in dotnet/corert#8323).

```
  C:\Users\michals\.nuget\packages\microsoft.netcore.app.runtime.nativeaot.linux-bionic-arm64\8.0.0-preview.6.23307.4/r
  untimes/linux-bionic-arm64/\native\libRuntime.WorkstationGC.a(MiscStubs.S.o): In function `RhpGetInlinedThreadStaticB
  ase':
  /__w/1/s/src/coreclr/nativeaot/Runtime/arm64/MiscStubs.S:12: undefined reference to `tls_InlinedThreadStatics'
  /__w/1/s/src/coreclr/nativeaot/Runtime/arm64/MiscStubs.S:12: undefined reference to `tls_InlinedThreadStatics'
  /__w/1/s/src/coreclr/nativeaot/Runtime/arm64/MiscStubs.S:12: undefined reference to `tls_InlinedThreadStatics'
  /__w/1/s/src/coreclr/nativeaot/Runtime/arm64/MiscStubs.S:12: undefined reference to `tls_InlinedThreadStatics'
```

Directory.Build.props

@@ -54,6 +54,7 @@
         - eng/native/build-commons.sh
         - src/native/libs/build-native.sh
         - src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/ObjectWriter.cs
+        - src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets
         - src/installer/pkg/sfx/bundle/shared-framework-distribution-template-x64.xml
         - src/installer/pkg/sfx/bundle/shared-framework-distribution-template-arm64.xml
      -->

src/coreclr/nativeaot/BuildIntegration/Microsoft.DotNet.ILCompiler.SingleEntry.targets

@@ -21,6 +21,7 @@
     <_targetPackageName>runtime.$(_targetOS)-$(_targetArchitecture).Microsoft.DotNet.ILCompiler</_targetPackageName>
 
     <!-- From this point onwards, we will treat linux-musl as linux -->
+    <_linuxLibcFlavor Condition="$(_targetOS.StartsWith('linux-'))">$(_targetOS.SubString(6))</_linuxLibcFlavor>
     <_targetOS Condition="$(_targetOS.StartsWith('linux'))">linux</_targetOS>
   </PropertyGroup>
 

src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.Unix.targets

@@ -42,6 +42,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <TargetTriple />
       <TargetTriple Condition="'$(CrossCompileArch)' != ''">$(CrossCompileArch)-linux-gnu</TargetTriple>
       <TargetTriple Condition="'$(CrossCompileArch)' != '' and ($(CrossCompileRid.StartsWith('linux-musl')) or $(CrossCompileRid.StartsWith('alpine')))">$(CrossCompileArch)-alpine-linux-musl</TargetTriple>
+      <TargetTriple Condition="'$(CrossCompileArch)' != '' and $(CrossCompileRid.StartsWith('linux-bionic'))">$(CrossCompileArch)-linux-android21</TargetTriple>
       <TargetTriple Condition="'$(CrossCompileArch)' != '' and ($(CrossCompileRid.StartsWith('freebsd')))">$(CrossCompileArch)-unknown-freebsd12</TargetTriple>
 
       <IlcRPath Condition="'$(IlcRPath)' == '' and '$(_IsApplePlatform)' != 'true'">$ORIGIN</IlcRPath>
@@ -64,7 +65,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <NetCoreAppNativeLibrary Include="System.Native" />
       <NetCoreAppNativeLibrary Include="System.Globalization.Native" Condition="'$(StaticICULinking)' != 'true' and '$(InvariantGlobalization)' != 'true'" />
       <NetCoreAppNativeLibrary Include="System.IO.Compression.Native" />
-      <NetCoreAppNativeLibrary Include="System.Net.Security.Native" Condition="!$(_targetOS.StartsWith('tvos'))" />
+      <NetCoreAppNativeLibrary Include="System.Net.Security.Native" Condition="!$(_targetOS.StartsWith('tvos')) and '$(_linuxLibcFlavor)' != 'bionic'" />
       <NetCoreAppNativeLibrary Include="System.Security.Cryptography.Native.Apple" Condition="'$(_IsApplePlatform)' == 'true'" />
       <!-- Not compliant for iOS-like platforms -->
       <NetCoreAppNativeLibrary Include="System.Security.Cryptography.Native.OpenSsl" Condition="'$(StaticOpenSslLinking)' != 'true' and '$(_IsiOSLikePlatform)' != 'true'" />
@@ -122,7 +123,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <LinkerArg Include="-lswiftCore" Condition="'$(_targetOS)' == 'osx'" />
       <LinkerArg Include="-lswiftFoundation" Condition="'$(_targetOS)' == 'osx'" />
       <LinkerArg Include="-lz" />
-      <LinkerArg Include="-lrt" Condition="'$(_IsApplePlatform)' != 'true'" />
+      <LinkerArg Include="-lrt" Condition="'$(_IsApplePlatform)' != 'true' and '$(_linuxLibcFlavor)' != 'bionic'" />
       <LinkerArg Include="-licucore" Condition="'$(_IsApplePlatform)' == 'true'" />
       <LinkerArg Include="-L/usr/lib/swift" Condition="'$(_targetOS)' == 'osx'" />
       <LinkerArg Include="@(StaticICULibs)" Condition="'$(StaticICULinking)' == 'true'" />
@@ -153,11 +154,16 @@ The .NET Foundation licenses this file to you under the MIT license.
       <LinkerArg Include="-Wl,--eh-frame-hdr" Condition="'$(_IsApplePlatform)' != 'true'" />
     </ItemGroup>
 
-    <Exec Command="command -v &quot;$(CppLinker)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low">
+    <PropertyGroup>
+      <_CommandProbe>command -v</_CommandProbe>
+      <_CommandProbe Condition="$([MSBuild]::IsOSPlatform('Windows'))">where</_CommandProbe>
+    </PropertyGroup>
+
+    <Exec Command="$(_CommandProbe) &quot;$(CppLinker)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low">
       <Output TaskParameter="ExitCode" PropertyName="_WhereLinker" />
     </Exec>
 
-    <Exec Command="command -v &quot;$(CppCompilerAndLinkerAlternative)&quot;" Condition="'$(CppCompilerAndLinkerAlternative)' != '' and '$(_WhereLinker)' != '0'" IgnoreExitCode="true" StandardOutputImportance="Low">
+    <Exec Command="$(_CommandProbe) &quot;$(CppCompilerAndLinkerAlternative)&quot;" Condition="'$(CppCompilerAndLinkerAlternative)' != '' and '$(_WhereLinker)' != '0'" IgnoreExitCode="true" StandardOutputImportance="Low">
       <Output TaskParameter="ExitCode" PropertyName="_WhereLinkerAlt" />
     </Exec>
 
@@ -189,11 +195,11 @@ The .NET Foundation licenses this file to you under the MIT license.
       <_LinkerVersion>$([System.Text.RegularExpressions.Regex]::Match($(_LinkerVersionString), '[1-9]\d*'))</_LinkerVersion>
     </PropertyGroup>
 
-    <Exec Command="command -v &quot;$(ObjCopyName)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low" Condition="'$(_IsApplePlatform)' != 'true' and '$(StripSymbols)' == 'true'">
+    <Exec Command="$(_CommandProbe) &quot;$(ObjCopyName)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low" Condition="'$(_IsApplePlatform)' != 'true' and '$(StripSymbols)' == 'true'">
       <Output TaskParameter="ExitCode" PropertyName="_WhereSymbolStripper" />
     </Exec>
 
-    <Exec Command="command -v &quot;$(ObjCopyNameAlternative)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low" Condition="'$(_IsApplePlatform)' != 'true' and '$(ObjCopyNameAlternative)' != '' and '$(StripSymbols)' == 'true'">
+    <Exec Command="$(_CommandProbe) &quot;$(ObjCopyNameAlternative)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low" Condition="'$(_IsApplePlatform)' != 'true' and '$(ObjCopyNameAlternative)' != '' and '$(StripSymbols)' == 'true'">
       <Output TaskParameter="ExitCode" PropertyName="_WhereSymbolStripperAlt" />
     </Exec>