Travis-CI: Shorten deb build log to keep it under 4 MB

There is a 4 MB hard limit on Travis-CI and build output needs to be less
than that. Silencing the 'make install' step gets rid of a lot of
"Installing.." and "Missing.." and removing all mysql-test files will
make the dh_missing warnings much shorter.

Cherry-picked from 41952c85.

debian/rules

@@ -121,8 +121,13 @@ endif
 	cp $(BUILDDIR)/support-files/mariadb.service debian/mariadb-server-10.2.mariadb.service
 	cp $(BUILDDIR)/support-files/mariadb@.service debian/mariadb-server-10.2.mariadb@.service
 
-	# make install
-	cd $(BUILDDIR) && $(MAKE) install DESTDIR=$(TMP)
+	# Run 'make install' without output since it is uninteresting and
+	# silencing it helps to make overall build log shorter and more readable
+	@echo "Running $(MAKE) install DESTDIR=$(TMP) ..."
+	cd $(BUILDDIR) && $(MAKE) install DESTDIR=$(TMP) > /dev/null
+
+	# If mariadb-test package is removed, also remove most of it's files
+	grep --quiet "Package: mariadb-test" debian/control || rm -rf $(TMP)/usr/share/mysql/mysql-test
 
 	# Delete runnable files we don't want to have in the test data package.
 	# This avoids triggering multiple Lintian errors.