googletest: Fix reversed +pthreads option (#12128)

If +pthreads is specified, googletest actually gets build without
pthreads support and vice versa.

If pthreads is not available, googletest should detect it itself which
is why "enabling" pthreads in case of ~pthreads does not seem to cause
any error.

Change-Id: I29de8c4a23dc3901124b27a1ead3354949b7e65b

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

@@ -38,7 +38,7 @@ def cmake_args(self):
             options = []
 
         options.append('-Dgtest_disable_pthreads={0}'.format(
-            'ON' if '+pthreads' in spec else 'OFF'))
+            'OFF' if '+pthreads' in spec else 'ON'))
         options.append('-DBUILD_SHARED_LIBS={0}'.format(
             'ON' if '+shared' in spec else 'OFF'))
         return options