[Build] Make sure we include CheckSymbolExists.

We need to include CheckSymbolExists on Windows as well as on Linux.

rdar://123381867

Author: al45tair

CoreFoundation/CMakeLists.txt

@@ -6,6 +6,9 @@ project(CoreFoundation
   VERSION 1338
   LANGUAGES ASM C)
 
+include(CheckSymbolExists)
+include(CheckIncludeFile)
+
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_C_STANDARD_REQUIRED YES)
 
@@ -70,8 +73,6 @@ if(CMAKE_SYSTEM_NAME STREQUAL Linux OR CMAKE_SYSTEM_NAME STREQUAL Android)
   add_compile_definitions($<$<COMPILE_LANGUAGE:C>:_GNU_SOURCE>)
 
   if(CMAKE_SYSTEM_NAME STREQUAL Linux)
-    include(CheckSymbolExists)
-    include(CheckIncludeFile)
     list(APPEND CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
     check_include_file("sched.h" HAVE_SCHED_H)
     if(HAVE_SCHED_H)