[CMake] add_llvm_library: Specify explicit suffix .imp to import library to avoid a warning between profile_rt-static and profile_rt-shared with lib/profile_rt.lib.

FIXME: It seems MS version of profile_rt.dll doesn't contain any export symbols.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188351 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
index 094969c..24afeea 100644
--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -12,6 +12,11 @@
 
   if( BUILD_SHARED_LIBS )
     llvm_config( ${name} ${LLVM_LINK_COMPONENTS} )
+    if (MSVC)
+      set_target_properties(${name}
+        PROPERTIES
+        IMPORT_SUFFIX ".imp")
+    endif ()
   endif()
 
   # Ensure that the system libraries always comes last on the