Rename the DLL import library "aom_dll.lib"

The new name makes the association with aom.dll more obvious than the
old name "aom_shared.lib". This is similar to the naming convention used
by MinGW (libfoo.dll.a) or Rust (foo.dll.lib).

Bug: aomedia:3476
Change-Id: I36a4db36fb67237e94f1db3b0042ce219446e559
(cherry picked from commit 140053ea86ddfc25271bb513ebfbcc4b7a01d37d)
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f999135..8f459f3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -291,7 +291,7 @@
     # Fix race condition on the export library file between the two versions.
     # Affects MSVC in all three flavors (stock, Clang/CL, LLVM-- the latter sets
     # MSVC and MINGW both to FALSE).
-    set_target_properties(aom PROPERTIES ARCHIVE_OUTPUT_NAME "aom_shared")
+    set_target_properties(aom PROPERTIES ARCHIVE_OUTPUT_NAME "aom_dll")
   if(NOT MSVC)