configure: enable -Wshorten-64-to-32 for hbd

Change-Id: I47bc4a1796ddce1a285942e19defcbefa2f6b275

build/cmake/aom_configure.cmake

@@ -136,9 +136,9 @@ else ()
   add_compiler_flag_if_supported("-Wuninitialized")
   add_compiler_flag_if_supported("-Wunused")
   add_compiler_flag_if_supported("-Wvla")
-  if (NOT CONFIG_HIGHBITDEPTH)
+  # TODO(jzern): this could be added as a cxx flags for test/*.cc only,
+  # avoiding third_party.
   add_c_flag_if_supported("-Wshorten-64-to-32")
-  endif ()
 
   # Add -Wshadow only for C files to avoid massive gtest warning spam.
   add_c_flag_if_supported("-Wshadow")

configure

@@ -722,12 +722,10 @@ process_toolchain() {
         fi
         # gtest makes heavy use of undefined pre-processor symbols
         check_cflags "-Wundef" && add_cflags_only "-Wundef"
-        if ! enabled highbitdepth; then
         # Avoid this warning for third_party C++ sources. Some reorganization
         # would be needed to apply this only to test/*.cc.
         check_cflags -Wshorten-64-to-32 && add_cflags_only -Wshorten-64-to-32
     fi
-    fi
 
     if enabled icc; then
         enabled werror && check_add_cflags -Werror