When building from git tags, the version number in `include/version.h`
is extracted from the output of `git describe`. While that is correct,
cmake was not configured to strip trailing whitespace from the command
output, which resulted in the version number being `12.5.1\n`.
That broke the generation of `include/version.h`, as the `\n` resulted
in the terminating quote being in a new line. This commit fixes that by
instructing cmake to strip trailing whitespace.
c19cbdf8d6