GMsh: Fix binary linking against its own libraries

GMsh binary now links against full path name of libraries. This fixes
problems, such as `dyld: Library not loaded: libGmsh.2.11.dylib`, when
running the executable.

var/spack/repos/builtin/packages/gmsh/package.py

@@ -62,7 +62,9 @@ def install(self, spec, prefix):
 
         build_directory = join_path(self.stage.path, 'spack-build')
         source_directory = self.stage.source_path
-        
+
+        options.append('-DCMAKE_INSTALL_NAME_DIR:PATH=%s/lib' % prefix)
+
         # Prevent GMsh from using its own strange directory structure on OSX
         options.append('-DENABLE_OS_SPECIFIC_INSTALL=OFF')