Deprecate devel/cpuflags

It's supposed to "return appropriate gcc flags to optimise compilation
for the current CPU", but it does not recognize modern CPUs.
MASTER_SITES is dead, no upstream is given in pkg-descr.

pkgsrc has a newer version 1.43 from 3 years ago, but for modern
compilers just using -march=native is probably a better alternative.

PR: 235993