Commit
d1dcc58323df745913b27e83dcc0f513780702a1
by Pau Espin PedrolMakefile: Support overriding LIBOSMOCORE_BRANCH
gr-gsm-master is using it but it cannot be overriden. Similarly iy can
be helpful to do so in temporarliy modified images when testing
libosmocore features.
Change-Id: Ia9f26f3513da339d2255a0f6b2277682fe15bdf2
