This fixes compilation failures during 'make tests' on ubuntu
due to unresolved symbols. ok?

diff /home/stsp/src/got-portable
commit - a8fa2ba8469e013475c403304989843b7fc17ae8
path + /home/stsp/src/got-portable
blob - c74afb7fe094b2cb7333d4a7d6c2ff4dcf423596
file + Makefile.am
--- Makefile.am
+++ Makefile.am
@@ -79,10 +79,13 @@ regress-fetch:
 	$(CC) $(DEFS) $(AM_CFLAGS) $(AM_CPPFLAGS) \
 		-o $(top_builddir)/regress/fetch/fetch_test \
 		$(top_srcdir)/regress/fetch/fetch_test.c \
+		$(top_srcdir)/lib/buf.c \
+		$(top_srcdir)/lib/date.c \
 		$(top_srcdir)/lib/error.c \
 		$(top_srcdir)/lib/privsep.c \
 		$(top_srcdir)/lib/reference.c \
 		$(top_srcdir)/lib/sha1.c \
+		$(top_srcdir)/lib/sigs.c \
 		$(top_srcdir)/lib/object.c \
 		$(top_srcdir)/lib/object_parse.c \
 		$(top_srcdir)/lib/path.c \