Disable file locks on Tiger

The new file lock feature depends on ruby's File.flock and
Pathname#flock, which aren't available on ruby 1.8.2.

If possible, they will eventually be reenabled after flock is
backported.

Library/Homebrew/formula.rb

@@ -229,6 +229,10 @@ def brew
   end
 
   def lock
+    # ruby 1.8.2 doesn't implement flock
+    # TODO backport the flock feature and reenable it
+    return if MacOS.version == :tiger
+
     HOMEBREW_CACHE_FORMULA.mkpath
     lockpath = HOMEBREW_CACHE_FORMULA/"#{@name}.brewing"
     @lockfile = lockpath.open(File::RDWR | File::CREAT)

Library/Homebrew/formula_installer.rb

@@ -492,6 +492,10 @@ def hold_locks?
   end
 
   def lock
+    # ruby 1.8.2 doesn't implement flock
+    # TODO backport the flock feature and reenable it
+    return if MacOS.version == :tiger
+
     if (@@locked ||= []).empty?
       f.recursive_dependencies.each do |dep|
         @@locked << dep.to_formula

Library/Homebrew/keg.rb

@@ -62,6 +62,10 @@ def fname
   end
 
   def lock
+    # ruby 1.8.2 doesn't implement flock
+    # TODO backport the flock feature and reenable it
+    yield if MacOS.version == :tiger
+
     HOMEBREW_CACHE_FORMULA.mkpath
     path = HOMEBREW_CACHE_FORMULA/"#{fname}.brewing"
     file = path.open(File::RDWR | File::CREAT)