sysutils/pesign: Deprecate and use GCC 10

• Unmaintaned since 2016.
• Very much out of date.
• Does not build with GCC 11 [1]: set USE_GCC=10 so that the port does not block GCC default version update to GCC 11 while waiting for expiration.

PR: 263544 [1]
Reported by: exp-run (antoine@) [1]
Approved by: gerald (mentor)
Differential Revision: https://reviews.freebsd.org/D35086