Prefer ${SRCTOP}/foo over ${.CURDIR}/../../foo and ${SRCTOP}/usr.bin/foo
over ${.CURDIR}/../foo for paths in Makefiles.
Differential Revision: https://reviews.freebsd.org/D9932
Sponsored by: Netflix
Silence on: arch@ (twice)
cat ${.ALLSRC} > ${.TARGET}
rather than
ln -sf ${.ALLSRC} ${.TARGET}
not to depends on absolute-path of symbolic links.
Commented by: marcel, obrien, bde
