Some distro may add their own prefix to the version string of clang, for
example in Ubuntu:
$ clang --version
Ubuntu clang version 17.0.5 (1ubuntu1)
...
That triggers the following meson error during the setup phase:
meson.build:25:44: ERROR: String '' cannot be converted to int
Change the regexp used to evaluate the clang version to avoid this
build failure.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
