Don't define _WIN32_IE or _WIN32_WINNT except on Windows builds


git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4516 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/CMakeLists.txt b/CMakeLists.txt
index fb4e713..95153a7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -89,12 +89,14 @@
 endif()
 
 # Minimum version is Windows 2000 (5.0)
-if(NOT CMAKE_SIZEOF_VOID_P MATCHES 8)
-  add_definitions(-D_WIN32_IE=0x0500 -D_WIN32_WINNT=0x0500)
-else()
-  # Win64 doesn't like us requesting a Windows version that didn't have
-  # 64-bit support. Request XP (5.1) instead.
-  add_definitions(-D_WIN32_IE=0x0501 -D_WIN32_WINNT=0x0501)
+if(WIN32)
+  if(NOT CMAKE_SIZEOF_VOID_P MATCHES 8)
+    add_definitions(-D_WIN32_IE=0x0500 -D_WIN32_WINNT=0x0500)
+  else()
+    # Win64 doesn't like us requesting a Windows version that didn't have
+    # 64-bit support. Request XP (5.1) instead.
+    add_definitions(-D_WIN32_IE=0x0501 -D_WIN32_WINNT=0x0501)
+  endif()
 endif()
 
 if(CMAKE_SIZEOF_VOID_P MATCHES 8)