Patch buildroots libcurl makefile, so it uses the cacert bundle.

Assumes ca-certificates is selected. (Manual!)

--- a/package/libcurl/libcurl.mk	2024-09-11 20:35:52.369995331 +0200
+++ b/package/libcurl/libcurl.mk	2024-09-08 20:40:51.393654807 +0200
@@ -83,10 +83,11 @@
 LIBCURL_CONF_OPTS += --without-gnutls
 endif
 
 ifeq ($(BR2_PACKAGE_LIBCURL_MBEDTLS),y)
 LIBCURL_CONF_OPTS += --with-mbedtls=$(STAGING_DIR)/usr
+LIBCURL_CONF_OPTS += --with-ca-bundle=/etc/ssl/certs/ca-certificates.crt
 LIBCURL_DEPENDENCIES += mbedtls
 else
 LIBCURL_CONF_OPTS += --without-mbedtls
 endif