graphics/jp2a: Give the port a makeover

Use the release archive to remove USES=autoreconf. Eliminate
CONFIGURE_ENV, MAKE_ENV, USE_CSTD, and LDFLAGS, as they are no longer
needed for this port. Add USES=localbase:ldflags and --disable-assert to
CONFIGURE_ARGS.

PR: 282336
Reported by: diizzy