Remove intermediate exception in Formula#system

Now that ErrorDuringExecution is only raised in one place, we can just
raise the BuildError directly instead.
ffmpeg --devel 2.1
libmpd: move URL from SourceForge.

Tarballs have been removed from SourceForge and are now hosted directly by musicpd.org.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
mpdscribble: move URL from SourceForge.

Tarballs have been removed from SourceForge and are now hosted directly by musicpd.org.

Closes #23915.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>
ledger: remove unneeded HEAD patch.

The patch has been pushed upstream, so it is not needed any longer.

Closes #23903.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>