Make these methods on ENV.

Library/Homebrew/extend/ENV.rb

@@ -18,15 +18,15 @@ module HomebrewEnvExtension
       self['CMAKE_PREFIX_PATH'] = "#{HOMEBREW_PREFIX}"
     end
 
-    if MACOS_VERSION >= 10.6 and (self['HOMEBREW_USE_CLANG'] or ARGV.include? '--use-clang')
+    if MACOS_VERSION >= 10.6 and self.use_clang?
       self['CC'] = "#{MacOS.xcode_prefix}/usr/bin/clang"
       self['CXX'] = "#{MacOS.xcode_prefix}/usr/bin/clang++"
       cflags = ['-O3'] # -O4 makes the linker fail on some formulae
-    elsif MACOS_VERSION >= 10.6 and (self['HOMEBREW_USE_LLVM'] or ARGV.include? '--use-llvm')
+    elsif MACOS_VERSION >= 10.6 and self.use_llvm?
       self['CC'] = "#{MacOS.xcode_prefix}/usr/bin/llvm-gcc"
       self['CXX'] = "#{MacOS.xcode_prefix}/usr/bin/llvm-g++"
       cflags = ['-O4'] # link time optimisation baby!
-    elsif MACOS_VERSION >= 10.6 and (self['HOMEBREW_USE_GCC'] or ARGV.include? '--use-gcc')
+    elsif MACOS_VERSION >= 10.6 and self.use_gcc?
       self['CC'] = "#{MacOS.xcode_prefix}/usr/bin/gcc"
       self['CXX'] = "#{MacOS.xcode_prefix}/usr/bin/g++"
       cflags = ['-O3']
@@ -292,4 +292,14 @@ Please take one of the following actions:
     remove 'CFLAGS', f
     remove 'CXXFLAGS', f
   end
+
+  def use_clang?
+    self['HOMEBREW_USE_CLANG'] or ARGV.include? '--use-clang'
+  end
+  def use_gcc?
+    self['HOMEBREW_USE_GCC'] or ARGV.include? '--use-gcc'
+  end
+  def use_llvm?
+    self['HOMEBREW_USE_LLVM'] or ARGV.include? '--use-llvm'
+  end
 end