make a regress-binaries target

Easier to build all the regression/unit test binaries in one pass
than going through all of ${REGRESS_BINARIES}
diff --git a/Makefile.in b/Makefile.in
index 84c3c6c..139e20a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -516,8 +516,7 @@
 	$(LD) -o $@ $(LDFLAGS) $(MISC_KEX_FUZZ_OBJS) \
 	    -lssh -lopenbsd-compat -lssh -lopenbsd-compat $(LIBS)
 
-REGRESS_BINARIES=\
-	regress/modpipe$(EXEEXT) \
+regress-binaries: regress/modpipe$(EXEEXT) \
 	regress/setuid-allowed$(EXEEXT) \
 	regress/netcat$(EXEEXT) \
 	regress/check-perm$(EXEEXT) \
@@ -528,7 +527,7 @@
 	regress/unittests/kex/test_kex$(EXEEXT) \
 	regress/misc/kexfuzz/kexfuzz$(EXEEXT)
 
-tests interop-tests t-exec: regress-prep $(TARGETS) $(REGRESS_BINARIES)
+tests interop-tests t-exec: regress-prep regress-binaries $(TARGETS)
 	BUILDDIR=`pwd`; \
 	TEST_SSH_SCP="$${BUILDDIR}/scp"; \
 	TEST_SSH_SSH="$${BUILDDIR}/ssh"; \