Fixed an error where gcc was available, but brew failed because it …

…has checked for XCode presence

The error was: "undefined method `<' for nil:NilClass", coming from Library/Homebrew/extend/ENV.rb:140

This prevented installing for users who have downloaded "standalone" compilers
eg. from <https://github.com/kennethreitz/osx-gcc-installer>.

Library/Homebrew/cmd/doctor.rb

@@ -195,6 +195,8 @@ def check_gcc_versions
   end
 
   if MacOS.xcode_version == nil
+      # TODO: Do better detection of gcc etc., or display proper instructions for
+      # installing eg. <https://github.com/kennethreitz/osx-gcc-installer>
       puts <<-EOS.undent
         We couldn't detect any version of Xcode.
         If you downloaded Xcode 4.1 from the App Store, you may need to run the installer.

Library/Homebrew/extend/ENV.rb

@@ -120,10 +120,10 @@ def gcc_4_0_1
   alias_method :gcc_4_0, :gcc_4_0_1
 
   def gcc
-    if MacOS.xcode_version < '4'
+    if MacOS.xcode_version.to_s < '4'
       self['CC'] = '/usr/bin/cc'
       self['CXX'] = '/usr/bin/c++'
-    elsif MacOS.xcode_version >= '4.2'
+    elsif MacOS.xcode_version.to_s >= '4.2'
       # Apple stopped adding the -4.2 suffixes
       self['CC']  = "#{MacOS.xcode_prefix}/usr/bin/gcc"
       self['CXX']  = "#{MacOS.xcode_prefix}/usr/bin/g++"
@@ -137,9 +137,9 @@ def gcc
   alias_method :gcc_4_2, :gcc
 
   def llvm
-    if MacOS.xcode_version < '4'
+    if MacOS.xcode_version.to_s < '4'
       self.gcc
-    elsif MacOS.xcode_version < '4.1'
+    elsif MacOS.xcode_version.to_s < '4.1'
       self['CC'] = "#{MacOS.xcode_prefix}/usr/bin/llvm-gcc"
       self['CXX'] = "#{MacOS.xcode_prefix}/usr/bin/llvm-g++"
     else
@@ -149,7 +149,7 @@ def llvm
   end
 
   def clang
-    if MacOS.xcode_version > '4'
+    if MacOS.xcode_version.to_s > '4'
       self['CC'] = "#{MacOS.xcode_prefix}/usr/bin/clang"
       self['CXX'] = "#{MacOS.xcode_prefix}/usr/bin/clang++"
     else