[binutils-gdb] Fix the triplet regexp to recognize triplets, not only quadruplets

[sergiodj+buildbot@redhat.com]

*** TEST RESULTS FOR COMMIT 71b30f27af091a16e6277e18ef574e0d2c0c55ef ***

Author: Matthias Klose <doko@ubuntu.com>
Branch: master
Commit: 71b30f27af091a16e6277e18ef574e0d2c0c55ef

Fix the triplet regexp to recognize triplets, not only quadruplets
This allows triplets where the vendor is not set.

gdb/ChangeLog:
2015-03-31  Matthias Klose  <doko@ubuntu.com>

	* compile/compile.c (compile_to_object): Allow triplets with or
	without vendor set.