Revert "ENV.rb: Always return integers from make_jobs"

This reverts commit ea1a9e603abe3dab90bf5b157d2614cf58e2cc8e.

Argh. Unrelated PySide changes slipped in.

Library/Homebrew/extend/ENV.rb

@@ -432,7 +432,7 @@ Please take one of the following actions:
   def make_jobs
     # '-j' requires a positive integral argument
     if self['HOMEBREW_MAKE_JOBS'].to_i > 0
-      self['HOMEBREW_MAKE_JOBS'].to_i
+      self['HOMEBREW_MAKE_JOBS']
     else
       Hardware.processor_count
     end