src/Makefile.am: fix osmo-gapk LDADD dependency

This change fixes parallel building problem, when osmo-gapk was
being compiled before its libosmogapk dependency:

  make[2]: *** No rule to make target '../src/libosmogapk.la',
               needed by 'osmo-gapk'.  Stop.
  make[2]: *** Waiting for unfinished jobs....

For some reason, automake ignores a dependency if the full
path is provided:

  $(top_builddir)/src/libosmogapk.la

while the relative path solves the problem:

  libosmogapk.la

Closes: OS#2907
Change-Id: I3fdd1731bd372bbb42fe57981e757386e8ede0f0
1 file changed