Fix cpp-linter tests to avoid .git dependency

Makes sure tests also pass when working from an archive rather than a
git clone.

Author: tautschnig

regression/cpp-linter/Makefile

@@ -1,10 +1,10 @@
 default: tests.log
 
 test:
-	@../test.pl -p -c ../../../scripts/cpplint.py
+	@../test.pl -p -c '../../../scripts/cpplint.py --repository=../../../'
 
 tests.log: ../test.pl
-	@../test.pl -p -c ../../../scripts/cpplint.py
+	@../test.pl -p -c '../../../scripts/cpplint.py --repository=../../../'
 
 clean:
 	find . -name '*.out' -execdir $(RM) '{}' \;