configure: make version_ge more tolerant of shady version input

When checking GDB versions we have to tolerate all sorts of random
distro extensions to the version string. While we already attempt to
do some of that before we call version_ge is makes sense to try and
regularise the first input by stripping extraneous -'s. While we at it
convert the old-style shell quoting into a cleaner form t shut up my
editors linter lest it confuse me by underlining the whole line.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20210202134001.25738-8-alex.bennee@linaro.org>