libminijail_unittest: add some tests

Adds libminijail_unittest with some very basic tests. More tests will
be added, but this gets all the pieces in place.

TEST=itself! [ FEATURES="test noclean" emerge-x86-alex chromeos-minijail ]
BUG=chromium-os:20917

Change-Id: I5893c6f72d1e741dd6287acde52af65500b059e4
Reviewed-on: http://gerrit.chromium.org/gerrit/8371
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Elly Jones <ellyjones@chromium.org>
Tested-by: Will Drewry <wad@chromium.org>
diff --git a/Makefile b/Makefile
index 37e99d9..afde282 100644
--- a/Makefile
+++ b/Makefile
@@ -13,11 +13,17 @@
 libminijail.so : libminijail.o libsyscalls.gen.o
 	$(CC) $(CFLAGS) -shared -o $@ $^ -lcap
 
+libminijail_unittest : libminijail_unittest.o libminijail.o libsyscalls.gen.o
+	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ -lcap
+
 libminijailpreload.so : libminijailpreload.c libsyscalls.gen.o libminijail.o
 	$(CC) $(CFLAGS) -shared -o $@ $^ -ldl -lcap
 
 libminijail.o : libminijail.c libminijail.h
 
+libminijail_unittest.o : libminijail_unittest.c test_harness.h
+	$(CC) $(CFLAGS) -c -o $@ $<
+
 libsyscalls.gen.o : libsyscalls.gen.c libsyscalls.h
 
 # sed expression which extracts system calls that are
@@ -61,4 +67,5 @@
 
 clean :
 	@rm -f libminijail.o libminijailpreload.so minijail0
+	@rm -f libminijail_unittest libminijail_unittest.o
 	@rm -f libsyscalls.gen.c libsyscalls.gen.o