libcurl: add nghttp2 optional dependency

The nghttp2 package has recently been added to buildroot. When
enabled, this adds support for HTTP2 to libcurl.

By default, libcurl configure script will enable HTTP2 if the library
is found using pkg-config. Adding this option makes the build
consistent.

Signed-off-by: Michaël Burtin <michael.burtin@netgem.com>
Signed-off-by: Anisse Astier <anisse.astier.ext@netgem.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/libcurl/libcurl.mk

@@ -88,6 +88,13 @@ else
 LIBCURL_CONF_OPTS += --without-brotli
 endif
 
+ifeq ($(BR2_PACKAGE_NGHTTP2),y)
+LIBCURL_DEPENDENCIES += nghttp2
+LIBCURL_CONF_OPTS += --with-nghttp2
+else
+LIBCURL_CONF_OPTS += --without-nghttp2
+endif
+
 define LIBCURL_FIX_DOT_PC
 	printf 'Requires: openssl\n' >>$(@D)/libcurl.pc.in
 endef