Greg Becker cfb6f21236 externals: allow package prefs to configure default not buildable (#16735) ... Allows `all` to be configured non-buildable in packages.yaml. The following config would only allow zlib to be built by Spack, all other packages would have to be found as externals. ``` packages: all: buildable: False zlib: buildable: True ```		2020-05-20 17:09:07 -07:00
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spack	externals: allow package prefs to configure default not buildable (#16735)	2020-05-20 17:09:07 -07:00