devel/stlink: Fix build on 32 bit platforms

• Remove settings of optimization from cmake/modules/c_flags.cmake as per section 13.9 of Porter's Handbook
• Switch to DISTVERSION
• Pet portclippy
• Reformat Makefile with portfmt

PR: 257708
Approved by: maitainer timeout (> 1 month)
Differential Revision: https://reviews.freebsd.org/D32545