Always call Process.wait with an argument

Library/Homebrew/formula.rb

@@ -572,7 +572,7 @@ class Formula
     logfn = "#{logd}/%02d.%s" % [@exec_count, File.basename(cmd).split(' ').first]
     mkdir_p(logd)
 
-    fork do
+    pid = fork do
       ENV['HOMEBREW_CC_LOG_PATH'] = logfn
 
       # TODO system "xcodebuild" is deprecated, this should be removed soon.
@@ -603,7 +603,7 @@ class Formula
         puts buf if ARGV.verbose?
       end
 
-      Process.wait
+      Process.wait(pid)
 
       $stdout.flush
 

Library/Homebrew/utils.rb

@@ -84,8 +84,8 @@ def interactive_shell f=nil
     ENV['HOMEBREW_DEBUG_INSTALL'] = f.name
   end
 
-  fork {exec ENV['SHELL'] }
-  Process.wait
+  Process.wait fork { exec ENV['SHELL'] }
+
   unless $?.success?
     puts "Aborting due to non-zero exit status"
     exit $?