fixup: fix make command to make coverity_scan work.

.travis.yml

@@ -115,7 +115,7 @@ matrix:
 
         # The command that will be added as an argument to "cov-build" to compile your project for analysis,
         # ** likely specific to your build **
-        build_command: make > /dev/null
+        build_command: make
 
         # Pattern to match selecting branches that will run analysis. We recommend leaving this set to 'coverity_scan'.
         # Take care in resource usage, and consider the build frequency allowances per