cross-compilation to Android fails due to strict compiler check

[johanvos]

Describe GraalVM and your environment :

• GraalVM version or commit id if built from source: 20.1-dev
• CE or EE: CE
• Build Time or run time failure: buld-time
• JDK version: JDK 11
• Native compiler information:
  Run the following to capture compiler version

  • In windows: cl.exe
  • In macOS : cc -v
  • In Linux: gcc --version

cross-compilation from Linux AMD64 for Android AArch64 fails, since NativeImageGenerator will invoke LinuxCCompilerInvoker.verifyCompiler to see if the build compiler is ok for the target.
When using LLVM though, we don't rely on this build compiler.

I propose to skip this step if the LLVM backend is used.