xcode-select check: move after first options

Library/brew.rb

@@ -16,22 +16,6 @@ $:.unshift(HOMEBREW_LIBRARY_PATH + '/vendor')
 $:.unshift(HOMEBREW_LIBRARY_PATH)
 require 'global'
 
-# Check for bad xcode-select before anything else, because `doctor` and
-# many other things will hang
-# Note that this bug was fixed in 10.9
-if `xcode-select -print-path 2>/dev/null`.chomp == '/' && MacOS.version < :mavericks
-  ofail <<-EOS.undent
-  Your xcode-select path is currently set to '/'.
-  This causes the `xcrun` tool to hang, and can render Homebrew unusable.
-  If you are using Xcode, you should:
-    sudo xcode-select -switch /Applications/Xcode.app
-  Otherwise, you should:
-    sudo rm -rf /usr/share/xcode-select
-  EOS
-
-  exit 1
-end
-
 case ARGV.first when '-h', '--help', '--usage', '-?', 'help', nil
   require 'cmd/help'
   puts Homebrew.help_s
@@ -47,6 +31,22 @@ when '-v'
   exit 0 if ARGV.length == 1
 end
 
+# Check for bad xcode-select before anything else, because `doctor` and
+# many other things will hang
+# Note that this bug was fixed in 10.9
+if OS.mac? && `xcode-select -print-path 2>/dev/null`.chomp == '/' && MacOS.version < :mavericks
+  ofail <<-EOS.undent
+  Your xcode-select path is currently set to '/'.
+  This causes the `xcrun` tool to hang, and can render Homebrew unusable.
+  If you are using Xcode, you should:
+    sudo xcode-select -switch /Applications/Xcode.app
+  Otherwise, you should:
+    sudo rm -rf /usr/share/xcode-select
+  EOS
+
+  exit 1
+end
+
 case HOMEBREW_PREFIX.to_s when '/', '/usr'
   # it may work, but I only see pain this route and don't want to support it
   abort "Cowardly refusing to continue at this prefix: #{HOMEBREW_PREFIX}"