cerbero: Add a new version URL identifier %(maj_ver)s

For use in URLs that use the first two version components in the URL.

https://bugzilla.gnome.org/show_bug.cgi?id=797330

cerbero/build/source.py

@@ -68,7 +68,8 @@ class Source (object):
         if name.startswith('gst') and name.endswith('-1.0'):
             # gst-libav-1.0, etc is useless for substitution, convert to 'gst-libav'
             name = name[:-4]
-        return string % {'name': name, 'version': self.version}
+        maj_ver = '.'.join(self.version.split('.')[0:2])
+        return string % {'name': name, 'version': self.version, 'maj_ver': maj_ver}
 
 
 class CustomSource (Source):

recipes/gnutls.recipe

@@ -6,8 +6,7 @@ from cerbero.utils import needs_xcode8_sdk_workaround
 class Recipe(recipe.Recipe):
     name = 'gnutls'
     version = '3.5.18'
-    maj_ver = '.'.join(version.split('.')[0:2])
-    url = 'https://www.gnupg.org/ftp/gcrypt/{0}/v{1}/{0}-{2}.tar.xz'.format(name, maj_ver, version)
+    url = 'https://www.gnupg.org/ftp/gcrypt/%(name)s/v%(maj_ver)s/%(name)s-%(version)s.tar.xz'
     tarball_checksum = 'ae2248d9e78747cf9c469dde81ff8f90b56838b707a0637f3f7d4eee90e80234'
     stype = SourceType.TARBALL
     # main library is LGPLv2+ and binaries is GPLv3+ and defined below