Don't build LLVM tools by default
Don't build LLVM tools by default

Most llvm are not required by llpc tests but take significant time
to compile and consume a lot of disk space.

This is as follow up commit to: https://github.com/GPUOpen-Drivers/llpc/pull/889.

GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc