build: cause the "check" rule to depend on $(PROGRAMS)

Summary:
* Makefile (check): Cause "make check" to build all $(PROGRAMS),
so that it verifies that the few benchmark-only source files that
not already built via "make check" do compile and link successfully.

Test Plan:
run "make clean; make check", and verify that
table/table_reader_bench.cc is now compiled.
Before, it was not, which led to an incomplete fix
for a build break.

Reviewers: ljin, igor.sugak, rven, igor, sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D35883

Makefile

@@ -328,7 +328,7 @@ coverage:
 	# Delete intermediate files
 	find . -type f -regex ".*\.\(\(gcda\)\|\(gcno\)\)" -exec rm {} \;
 
-check: $(TESTS) ldb
+check: $(TESTS) $(PROGRAMS)
 	for t in $(TESTS); do echo "***** Running $$t"; ./$$t || exit 1; done
 	python tools/ldb_test.py