make.sh: Explicitely check the source tarballs

make.sh: Explicitely check the source tarballs

The Makefiles do not automatically perform the check that I expected
them to perform when running a build. They check if the source tarballs
are all present, but they don't check whether they match the checksum.
This is only being done when "./make.sh downloadsrc" is being run.

In case of the automated builds, we explicitely run "./make.sh
downloadsrc", so I don't think that this might have introduced any
malicious source into the published builds.

Reported-by: Stephen Cuka <stephen@firemypi.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>