test/Makefile: Run tests with prove when available

Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

test/Makefile

 T = $(sort $(wildcard *.t))
 
+PROVE := $(shell command -v prove 2> /dev/null)
+
+ifdef PROVE
+check:
+	prove .
+else
 check: $(T)
+endif
 
 clean:
 	$(RM) -r test-results/