gsl: drop libtool file. (This did not reach #2700...)
gsl: drop libtool file. (This did not reach #2700...)

While at it, add cmd:pkg_config to TEST_REQUIRES as one test was
being skipped. (Now all tests succeed :)

Begasus/haikuports,moochris/haikuports,haikuports/haikuports,haikuports/haikuports,Begasus/haikuports,moochris/haikuports,haikuports/haikuports,nielx/haikuports,Begasus/haikuports,Begasus/haikuports,Begasus/haikuports,moochris/haikuports,nielx/haikuports,nielx/haikuports,haikuports/haikuports,haikuports/haikuports