libglib2: improve dev file handling

libglib2: improve dev file handling

Remove source schema files from target
(/usr/share/glib-2.0/schemas/*.dtd and *.xml) at target finalization
time.
This is because other packages install schemas as well to avoid
duplicating file removal efforts all around.

Add a schema compiler run on target finalization as well - we previously
didn't do this since not many packages use it, however the upcoming
connman-gtk package does require a valid gschemas.compiled to work
properly.
We also do this at target finalization to avoid each package handling
this on their own.

Purge some extra binaries and files from the target, like the schema
compiler to save additional space since they're unused at run time.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>