build: Fix crypto reference in Makefile_am

Use CRYPTO_LIBS, as LIBCRYPT is undefined.

Change-Id: I603ec51067bb2bf5e9d030b9e6ff02dbbabae8f8
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/Makefile.am b/Makefile.am
index c9ce2ff..beda315 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -77,7 +77,7 @@
 	$(PHOSPHOR_LOGGING_LIBS) \
 	$(PHOSPHOR_DBUS_INTERFACES_LIBS) \
 	-lstdc++fs \
-	$(LIBPAM) $(LIBCRYPT) -lpam_misc -lssl \
+	$(LIBPAM) $(CRYPTO_LIBS) -lpam_misc -lssl \
 	-version-info 0:0:0 -shared
 libuserlayer_la_CXXFLAGS = \
 	$(SYSTEMD_CFLAGS) \