package/uacme: don't allow ualpn with mbedTLS

ualpn requires mbedTLS to be configured and built with
MBEDTLS_X509_ALLOW_UNSUPPORTED_CRITICAL_EXTENSION
which is not the default and can be a security risk.

Therefore make BR2_PACKAGE_UACME_UALPN depend on
BR2_PACKAGE_OPENSSL || BR2_PACKAGE_GNUTLS.

Fixes http://autobuild.buildroot.net/results/d241121f8155bad9b6b25c16234576abb7fc940b

See also

https://github.com/ndilieto/uacme/issues/23
https://github.com/ARMmbed/mbedtls/issues/3241
https://github.com/ARMmbed/mbedtls/pull/3243
http://lists.busybox.net/pipermail/buildroot/2020-April/281059.html
http://lists.busybox.net/pipermail/buildroot/2020-April/281108.html

Signed-off-by: Nicola Di Lieto <nicola.dilieto@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 96c3b52132b41716ca445b4c73a1a8886c26e5ee)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/uacme/Config.in

@@ -19,6 +19,7 @@ if BR2_PACKAGE_UACME
 config BR2_PACKAGE_UACME_UALPN
 	bool "enable ualpn"
 	depends on BR2_TOOLCHAIN_HAS_THREADS
+	depends on BR2_PACKAGE_OPENSSL || BR2_PACKAGE_GNUTLS
 	select BR2_PACKAGE_LIBEV
 	help
 	  Build and install ualpn, the transparent proxying tls-alpn-01
@@ -27,4 +28,7 @@ config BR2_PACKAGE_UACME_UALPN
 comment "ualpn needs a toolchain w/ threads"
 	depends on !BR2_TOOLCHAIN_HAS_THREADS
 
+comment "ualpn needs either OpenSSL or GnuTLS"
+	depends on !(BR2_PACKAGE_OPENSSL || BR2_PACKAGE_GNUTLS)
+
 endif

package/uacme/uacme.mk

@@ -18,12 +18,12 @@ UACME_CONF_ENV = ac_cv_prog_cc_c99='-std=gnu99'
 ifeq ($(BR2_PACKAGE_GNUTLS),y)
 UACME_CONF_OPTS += --with-gnutls
 UACME_DEPENDENCIES += gnutls
-else ifeq ($(BR2_PACKAGE_MBEDTLS),y)
-UACME_CONF_OPTS += --with-mbedtls
-UACME_DEPENDENCIES += mbedtls
 else ifeq ($(BR2_PACKAGE_OPENSSL),y)
 UACME_CONF_OPTS += --with-openssl
 UACME_DEPENDENCIES += openssl
+else ifeq ($(BR2_PACKAGE_MBEDTLS),y)
+UACME_CONF_OPTS += --with-mbedtls
+UACME_DEPENDENCIES += mbedtls
 endif
 
 ifeq ($(BR2_PACKAGE_UACME_UALPN),y)