graphics/photoflow: fix build on GCC architectures, don't optimize for builder CPU

This port passes -march flags which are bad for users using packages.

Also merge https://github.com/aferrero2707/PhotoFlow/commit/0c79ee254eab9e4a44c7aeca9e43dc7990f14dd8#diff-2d5c4ed90f403ec79d56bb0af37dac07 and https://github.com/aferrero2707/PhotoFlow/commit/84c19b68d7a38dcf4877e7762303fb1841f33d3b#diff-2d5c4ed90f403ec79d56bb0af37dac07 for compatibility with GCC 9.

PR: 239833
Approved by: yuri (maintainer), linimon (mentor)
Differential Revision: https://reviews.freebsd.org/D21285