Makefile: clean up TEST_PROGRAMS definition

We try to keep lines under 80 characters, not to mention
that sticking a bunch of stuff on one line makes diffs
messier.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -1356,7 +1356,14 @@ endif
 
 ### Testing rules
 
-TEST_PROGRAMS = test-chmtime$X test-genrandom$X test-date$X test-delta$X test-sha1$X test-match-trees$X test-parse-options$X test-path-utils$X
+TEST_PROGRAMS += test-chmtime$X
+TEST_PROGRAMS += test-date$X
+TEST_PROGRAMS += test-delta$X
+TEST_PROGRAMS += test-genrandom$X
+TEST_PROGRAMS += test-match-trees$X
+TEST_PROGRAMS += test-parse-options$X
+TEST_PROGRAMS += test-path-utils$X
+TEST_PROGRAMS += test-sha1$X
 
 all:: $(TEST_PROGRAMS)