wolfssl: build with WOLFSSL_ALT_CERT_CHAINS

"Alternate certification chains, as oppossed to requiring full chain
validataion. Certificate validation behavior is relaxed, similar to
openssl and browsers. Only the peer certificate must validate to a trusted
certificate. Without this, all certificates sent by a peer must be
used in the trust chain or the connection will be rejected."

This fixes e.g. uclient-fetch and curl connecting to servers using a Let's
Encrypt certificate which are cross-signed by the now expired
DST Root CA X3, see [0].

This is the recommended solution from upstream [1].

The binary size increases by ~12.3kb:
1236160 staging_dir/target-mipsel_24kc_musl/usr/lib/libwolfssl.so.4.8.1.39c36f2f
1248704 staging_dir/target-mipsel_24kc_musl/usr/lib/libwolfssl.so.4.8.1.39c36f2f

[0] https://github.com/openwrt/packages/issues/16674
[1] https://github.com/wolfSSL/wolfssl/issues/4443#issuecomment-934926793

Signed-off-by: Andre Heider <a.heider@gmail.com>
[bump PKG_RELEASE]
Signed-off-by: David Bauer <mail@david-bauer.net>

package/libs/wolfssl/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=wolfssl
 PKG_VERSION:=4.8.1-stable
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://github.com/wolfSSL/wolfssl/archive/v$(PKG_VERSION)
@@ -59,7 +59,13 @@ define Package/libwolfssl/config
 	source "$(SOURCE)/Config.in"
 endef
 
-TARGET_CFLAGS += $(FPIC) -DFP_MAX_BITS=8192 -fomit-frame-pointer -flto
+TARGET_CFLAGS += \
+	$(FPIC) \
+	-fomit-frame-pointer \
+	-flto \
+	-DFP_MAX_BITS=8192 \
+	-DWOLFSSL_ALT_CERT_CHAINS
+
 TARGET_LDFLAGS += -flto
 
 # --enable-stunnel needed for OpenSSL API compatibility bits