Avoid UnboundLocalError

Make sure cdash_phase is defined before referring to it.

lib/spack/spack/reporters/cdash.py

@@ -77,6 +77,7 @@ def build_report(self, filename, report_data):
 
         # Parse output phase-by-phase.
         phase_regexp = re.compile(r"Executing phase: '(.*)'")
+        cdash_phase = ''
         for spec in report_data['specs']:
             for package in spec['packages']:
                 if 'stdout' in package: