[clang] [flang] [clang][driver] When -fveclib=ArmPL flag is in use, always link against libamath (PR #116432)

[Paul Osmialowski via cfe-commits]

pawosm-arm wrote:

> We probably have to provide a link to some documentation for libamath. May be something like the following one. https://developer.arm.com/documentation/102574/2410/Optimized-math-routines---libamath

I'm always anxious to provide a link that contains numeric ID (like the one, `102574/2410`) as it suggest a dynamically generated reference that may be outlived by the lifespan of the change we're introducing in this commit...

https://github.com/llvm/llvm-project/pull/116432