[cmake] [ARM] Exclude any VFP builtins if VFP is not supported
rL325492 disables FPU features when using soft floating point
(-mfloat-abi=soft), which is used internally when building for arm. This causes
errors with builtins that utililize VFP instructions.
With this change we check if VFP is enabled (by checking if the preprocessor
macro VFP_FP is defined), and exclude such builtins if it is not enabled.
Reviewers: rengolin, samsonov, compnerd, smeenai, javed.absar, peter.smith
Reviewed By: peter.smith
Subscribers: delcypher, peter.smith, mgorny, kristof.beyls, chrib, llvm-commits
Differential Revision: https://reviews.llvm.org/D47217