Pathname#install_metafiles: skip empty files.

Extracted from #10851

Library/Homebrew/extend/pathname.rb

@@ -432,6 +432,7 @@ class Pathname
   def install_metafiles(from = Pathname.pwd)
     Pathname(from).children.each do |p|
       next if p.directory?
+      next if File.zero?(p)
       next unless Metafiles.copy?(p.basename.to_s)
 
       # Some software symlinks these files (see help2man.rb)

Library/Homebrew/test/formula_installer_spec.rb

@@ -51,7 +51,8 @@ describe FormulaInstaller do
   specify "basic installation" do
     temporary_install(Testball.new) do |f|
       # Test that things made it into the Keg
-      expect(f.prefix/"readme").to exist
+      # "readme" is empty, so it should not be installed
+      expect(f.prefix/"readme").not_to exist
 
       expect(f.bin).to be_a_directory
       expect(f.bin.children.count).to eq(3)