Mk/bsd.commands.mk: Use absolute path to define GMAKE

Same as BSDMAKE variable. It is needed by some ports.

Some ports needed fixes:

• devel/rcs57: Regenerate configure with newer autoconf so it can deal with MAKE set to an absolute path. While here fix issues with (un)escaping double quotes. The warnings about this were in WRKSRC/src/conf.err.
• lang/gnu-cobol: Patch configure.ac so the MAKE environment variable can contain an absolute path, and define MAKE before it is used in AM_INIT_AUTOMAKE. Remove post-patch patching of configure. It appears to have been fixed upstream.
• math/unuran: Remove post-patch, fixed upstream.
• net-mgmt/kismet: Fix post-patch.

PR: 283534
Exp-run by: antoine