[Driver] Don't alias -mstrict-align to -mno-unaligned-access

GCC ports only supports one of the options, with -mstrict-align
preferred by newer ports. They reject adding -m[no-]unaligned-access to
newer ports that use -m[no-]strict-align.
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111555).

We should not support aliases, either. Since the behavior has been
long-time for ARM (a146a483), support
both forms for ARM for now but remove -m[no-]unaligned-access for
RISC-V/LoongArch (see also
https://github.com/riscv-non-isa/riscv-c-api-doc/pull/62).

While here, add TargetSpecific to ensure errors on unsupported targets
(https://reviews.llvm.org/D151590) and remove unneeded CC1 options.

Pull Request: https://github.com/llvm/llvm-project/pull/85350