[clang] [M68k][clang] Enable frame pointer optimization by default (PR #87264)

[Peter Lafreniere via cfe-commits]

n8pjl wrote:

This is a necessary change to make m68k clang competitive in performance to GCC,
and aligns with #88300.

Reviewed and tested the change. LGTM, but I'm not a maintainer.

https://github.com/llvm/llvm-project/pull/87264