Implement fails_with for non-Apple compilers

This adds support for non-Apple GCC compilers in the fails_with code.
A fails_with block for a non-Apple compiler looks like:

fails_with :gcc => '4.8.1' do
  cause 'Foo'
end

Non-Apple compilers don't have build numbers, so compiler failures are
based on version strings instead.

Internally non-Apple compilers can be distinguished because they are
passed around as strings instead of symbols.

In addition, this alters the priority list for compilers, with the
following changes:

* Apple GCC 4.2 and LLVM-GCC swap positions, with GCC now taking
  priority. (Maybe LLVM-GCC should just go away.)
* Non-Apple GCC compilers are ranked below GCC 4.2 but above LLVM-GCC
  and Apple GCC 4.0.

1 files changed, 10 insertions, 0 deletions

diff --git a/Library/Homebrew/extend/ENV/std.rb b/Library/Homebrew/extend/ENV/std.rb
index 67ab85952..e931b33ba 100644
--- a/Library/Homebrew/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/ENV/std.rb
@@ -167,6 +167,16 @@ module Stdenv
   end
   alias_method :gcc_4_2, :gcc
 
+  GNU_GCC_VERSIONS.each do |n|
+    define_method(:"gcc-4.#{n}") do
+      gcc = "gcc-4.#{n}"
+      self.cc = self['OBJC'] = gcc
+      self.cxx = self['OBJCXX'] = gcc.gsub('c', '+')
+      set_cpu_cflags
+      @compiler = gcc
+    end
+  end
+
   def llvm
     self.cc  = MacOS.locate("llvm-gcc")
     self.cxx = MacOS.locate("llvm-g++")