jobs/master-builds: archive core, testsuite.log

In case one of the master-buils is segfaulting or has an error in the
testsuite, collect the relevant files and store them as artifacts.

It was asked in the related issue to do this only on error, however
while there's an option to archive only artifacts when a build is
successful, there is not an option to do it only on failure. So just do
it always, the testsuite.log file is typically just a few kb in size.
core files should only get generated on error.

Closes: OS#5642
Change-Id: I91d4b995b16c8e028a5dff19b0e0f09c01d8c8c6

jobs/master-builds.yml

@@ -478,6 +478,9 @@
       - shell: '{obj:cmd}'
 
     publishers:
+       - archive:
+           allow-empty: true
+           artifacts: '**/core, **/testsuite.log'
        - warnings:
            console-log-parsers:
              - 'GNU C Compiler 4 (gcc)'