The valgrind analysis stage inherits from existing artefacts, so make
sure to reset the permissions on the glib build directory to avoid a new
build failing.

$ meson ${MESON_COMMON_OPTIONS} --werror -Dsystemtap=true -Ddtrace=true -Dfam=true -Dinstalled_tests=true _build
<snip>
PermissionError: [Errno 13] Permission denied: '/builds/GNOME/glib/_build/meson-logs/meson-log.txt'