[android] Fix build with newer NDK (#103233)

Newer versions of Android NDK (tested with 26.3) no longer include
support for 32-bit host machines and have moved libraries around for
that reason.  One of the libraries that changed its location is
`libclang.so`, required to build MonoVM for Android.

This PR adds support to detect the library at its new location.

src/mono/mono.proj

@@ -806,7 +806,8 @@ JS_ENGINES = [NODE_JS]
 
     <!-- Linux specific options -->
     <ItemGroup Condition="'$(AotHostOS)' == 'linux'">
-      <_LibClang Include="$(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/$(MonoToolchainPrebuiltOS)/lib64/libclang.so.*"/>
+      <_LibClang Include="$(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/$(MonoToolchainPrebuiltOS)/lib/libclang.so" Condition=" Exists('$(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/$(MonoToolchainPrebuiltOS)/lib/libclang.so') "/>
+      <_LibClang Include="$(ANDROID_NDK_ROOT)/toolchains/llvm/prebuilt/$(MonoToolchainPrebuiltOS)/lib64/libclang.so.*" Condition=" '$(_LibClang)' == '' "/>
     </ItemGroup>
     <PropertyGroup Condition="'$(TargetsLinux)' == 'true' and '$(Platform)' == 'arm64'">
       <MonoUseCrossTool>true</MonoUseCrossTool>