McdMaster: fail to build if umask() is missing
McdMaster: fail to build if umask() is missing

We ought to be able to rely on umask() for files created since 5.2.2,
at least on Unix.

Signed-off-by: Simon McVittie <2b470b34502dbf3ba4bcc04ea7e64f4e0e104f33@collabora.co.uk>
Reviewed-by: Xavier Claessens <6f61b6f8ca6f7cbeae6bb087ddf85cf85dce43eb@collabora.co.uk>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=54151

freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control