Remove redirect header from module to prevent excessive warnings

[rickmark]

Summary

This removes the redirect header from the module which emits warnings when module builds
occur. This also breaks the seperation of Support and TargetParser modules.

llvm/include/llvm/module.modulemap

module Support {
     requires cplusplus
 
     umbrella "Support"
     module * { export * }
 
     // Exclude this; it should only be used on Windows.
     exclude header "Support/Windows/WindowsSupport.h"
 
+    // Exclude this; it has been replaced by llvm/TargetParser/Host.h.
+    exclude header "Support/Host.h"
+
     // Exclude these; they are fundamentally non-modular.
     exclude header "Support/PluginLoader.h"
     exclude header "Support/Solaris/sys/regset.h"
     textual header "Support/TargetOpcodes.def"
 
   }
 
   module TargetParser {