git: Ignore .polyglot.build.properties files generated by maven build

These files are generated during a maven build. They are usually removed
automatically by maven after the build.

Git-ignore them because they are not meant to be under source control.

Change-Id: If0273c25d0a324413d17bfbd1d6059956f49c1c1
Signed-off-by: Marco Miller <marco.miller@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/c/tracecompass/org.eclipse.tracecompass/+/197773
Tested-by: Trace Compass Bot <tracecompass-bot@eclipse.org>
Tested-by: Bernd Hufmann <bernd.hufmann@ericsson.com>
Reviewed-by: Bernd Hufmann <bernd.hufmann@ericsson.com>

.gitignore

@@ -1,6 +1,7 @@
 # LC_COLLATE=C sort
 */.settings/org.sonar.ide.eclipse.core.prefs
 .DS_Store
+.polyglot.build.properties
 bin/
 target/
 workspace/