[CMake] add_llvm_library: don't use .imp suffix for import libraries on Windows (PR22334)

This was added in r188351 to fix a naming conflict between the
profile_rt-static and profile_rt-shared who both ended up in
lib/profile_rt.lib.

The change also affected other libraries (like libclang), and
users are reporting that they find it surprising that there's
no longer a libclang.lib. Since the profile_rt naming conflict
doesn't seem to exist any more, I think we can remove this.

Differential Revision: http://reviews.llvm.org/D7391

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228049 91177308-0d34-0410-b5e6-96231b3b80d8

cmake/modules/AddLLVM.cmake

@@ -334,11 +334,6 @@ function(llvm_add_library name)
         PREFIX ""
         )
     endif()
-    if (MSVC)
-      set_target_properties(${name}
-        PROPERTIES
-        IMPORT_SUFFIX ".imp")
-    endif ()
   endif()
 
   if(ARG_MODULE OR ARG_SHARED)