MF11 r352638,r358076: correct Clang and lld version checks

MF11 r352638,r358076: correct Clang and lld version checks

r352638 (mhorne): Allow for compiler versions >= 10
r358076 (dim): Correctly recognize linker versions greater than 10.0.

These routines determine the host compiler and linker version, and caused
attempts to build 12.1-RELEASE on 13-CURRENT to fail after the latter was
updated to Clang 10.  The host compiler version was also misdetected on
11.3 although it seems not to have caused the same build failure there.

We don't guarantee such a build config to work, but it is used by FreeBSD
ports build processes.  As a result the fixes from stable/11 will be
included with the next set of advisories, and are being committed to the
releng branch now to unblock ports builds.

PR:		245973
Reported by:	sbruno, antoine
Approved by:	so
Errata:		EN-20:10.build
Sponsored by:	The FreeBSD Foundation