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

[Kiran Chandramohan via cfe-commits]

kiranchandramohan 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

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