openblas: Run tests only when requested (#3370)

The tests fail on some systems (e.g. Comet at SDSC) that impose limits on the number of processes or threads one can run simultaneously on the head node. Thus the tests should not be run by default.

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

@@ -117,6 +117,7 @@ def build_targets(self):
 
         return self.make_defs + targets
 
+    @on_package_attributes(run_tests=True)
     @run_after('build')
     def check_build(self):
         make('tests', *self.make_defs)
@@ -129,6 +130,7 @@ def install_targets(self):
         ]
         return make_args + self.make_defs
 
+    @on_package_attributes(run_tests=True)
     @run_after('install')
     def check_install(self):
         spec = self.spec