- do_build: do not suppress --download-api-only option

Or was there a particular reason for not displaying this option in
"osc build -h"?

osc/commandline.py

@@ -5541,7 +5541,7 @@ def parse_repoarchdescr(self, args, noinit = False, alternative_project = None,
     @cmdln.option('--cpio-bulk-download', action='store_false',
                   dest='disable_cpio_bulk_download', help=SUPPRESS_HELP)
     @cmdln.option('--download-api-only', action='store_true',
-                  help=SUPPRESS_HELP)
+                  help='only fetch packages from the api')
     @cmdln.option('--oldpackages', metavar='DIR',
             help='take previous build from DIR (special values: _self, _link)')
     @cmdln.option('--shell', action='store_true',