[fuchsia-pkg] Whitelist packages with cmx

Whitelist all packages that have cmx's to be able to launch with bare
package URLs.

TESTED=
List generated with:
print(get_path_info(get_label_info(target_name,"dir"), "dir"))
in assert_cmx.gni when a cmx is found

fx set x64 --packages=garnet/packages/kitchen_sink,peridot/packages/kitchen_sink,topaz/packages/kitchen_sink

CF-156 #comment

Change-Id: I909a78f1bbdc351a1b5b94b707e70e366164a71b
1 file changed