graphics/libepoxy: update to 1.5.7

Changes: https://github.com/anholt/libepoxy/releases/tag/1.5.5
Changes: https://github.com/anholt/libepoxy/releases/tag/1.5.6
Changes: https://github.com/anholt/libepoxy/releases/tag/1.5.7
PR: 254350
Reported by: portscout
Submitted by: Evgeniy Khramtsov <2khramtsov@gmail.com> (based on)
Approved by: zeising