Fixed Xcode unit tests on non-Mac OSes

tests/actions/xcode/test_xcode4_project.lua

@@ -16,6 +16,7 @@
 
 	local sln, tr
 	function suite.setup()
+		_OS = "macosx"
 		_ACTION = "xcode4"
 		io.eol = "\n"
 		xcode.used_ids = { } -- reset the list of generated IDs

tests/actions/xcode/test_xcode_common.lua

@@ -12,7 +12,7 @@
 
 --
 -- Replacement for xcode.newid(). Creates a synthetic ID based on the node name,
--- it's intended usage (file ID, build ID, etc.) and its place in the tree. This 
+-- its intended usage (file ID, build ID, etc.) and its place in the tree. This 
 -- makes it easier to tell if the right ID is being used in the right places.
 --
 

tests/actions/xcode/test_xcode_project.lua

@@ -16,6 +16,7 @@
 
 	local sln, tr
 	function suite.setup()
+		_OS = "macosx"
 		_ACTION = "xcode3"
 		io.eol = "\n"
 		xcode.used_ids = { } -- reset the list of generated IDs