keg: try to avoid disk IO when possible

Calling Pathname#text_executable? reads in the first 1024 bytes of the
file, so try the basename check (which requires no filesystem access)
first.

Library/Homebrew/keg_fix_install_names.rb

@@ -181,7 +181,7 @@ class Keg
     # find name-config scripts, which can be all over the keg
     Pathname.new(self).find do |pn|
       next if pn.symlink? or pn.directory?
-      pkgconfig_files << pn if pn.text_executable? and pn.basename.to_s.end_with? '-config'
+      pkgconfig_files << pn if pn.basename.to_s.end_with? '-config' and pn.text_executable?
     end
     pkgconfig_files
   end