Add a "unit" target to run only unit tests.
diff --git a/Makefile.in b/Makefile.in
index e10f374..e1a6aa2 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -564,7 +564,7 @@
 	regress/unittests/utf8/test_utf8$(EXEEXT) \
 	regress/misc/kexfuzz/kexfuzz$(EXEEXT)
 
-tests interop-tests t-exec: regress-prep regress-binaries $(TARGETS)
+tests interop-tests t-exec unit: regress-prep regress-binaries $(TARGETS)
 	BUILDDIR=`pwd`; \
 	TEST_SSH_SCP="$${BUILDDIR}/scp"; \
 	TEST_SSH_SSH="$${BUILDDIR}/ssh"; \