It looks like we need base64 routines when compiling WPS in hostapd (used in src/wps/wps_registrar.c:910).
@@ -282,6 +282,7 @@ OBJS += ../src/wps/wps_registrar.o
NEED_DH_GROUPS=y
NEED_SHA256=y
NEED_CRYPTO=y
+NEED_BASE64=y
endif
ifdef CONFIG_EAP_IKEV2
@@ -526,6 +526,7 @@ endif
CONFIG_IEEE8021X_EAPOL=y