Move basedir to config file

Summary: This allows us to extend this more easily to server builds, too.

Reviewed By: lblasa

Differential Revision: D35901750

fbshipit-source-id: 7030846ad485d709cf4c2e95f0cad287f98b051b

packer/src/packlist.yaml

@@ -1,5 +1,6 @@
 mac:
   mode: exact
+  basedir: mac
   files:
     frameworks:
       - Flipper.app/Contents/Frameworks/
@@ -11,6 +12,7 @@ mac:
 
 linux:
   mode: glob
+  basedir: linux-unpacked
   files:
     frameworks:
       - '!resources/'
@@ -20,6 +22,7 @@ linux:
 
 windows:
   mode: glob
+  basedir: win-unpacked
   files:
     frameworks:
       - '!resources/'