doc: update depends doc to prefer .cmake outputs

Author: fanquake

depends/packages.md

@@ -153,8 +153,8 @@ Most autotools projects can be properly staged using:
 ## Build outputs:
 
 In general, the output of a depends package should not contain any libtool
-archives. Instead, the package should output `.pc` (`pkg-config`) files where
-possible.
+archives or `.pc` (`pkg-config`) files. Instead, the package should output
+`.cmake` (CMake) files where possible.
 
 From the [Gentoo Wiki entry](https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Handling_Libtool_Archives):