Link against just built zlib

Change-Id: Iebc12189c15a2342b2af68391c46281d4abbcb6d
diff --git a/git_static.go b/git_static.go
index bc5ebcb..96e8741 100644
--- a/git_static.go
+++ b/git_static.go
@@ -8,7 +8,8 @@
 #cgo LDFLAGS: -L${SRCDIR}/vendor/curl/build/lib -lcurl
 #cgo LDFLAGS: -L${SRCDIR}/vendor/boringssl/build/ssl -lssl
 #cgo LDFLAGS: -L${SRCDIR}/vendor/boringssl/build/crypto -lcrypto
-#cgo linux LDFLAGS: -lrt -lpthread -ldl -lz
+#cgo LDFLAGS: -L${SRCDIR}/vendor/zlib/build -lz
+#cgo linux LDFLAGS: -lrt -lpthread -ldl
 #cgo darwin LDFLAGS: -framework Security -framework CoreFoundation -lz -liconv
 #include <git2.h>