Fix cmake -E copy of CrashReporter.nib.

indra/mac_crash_logger/CMakeLists.txt was using 'cmake -E copy_directory' to
copy CrashReporter.nib -- which is actually a binary file. Apparently that
works, until CMake 3.12.0, which produces an error. Use copy_if_different
instead.

indra/mac_crash_logger/CMakeLists.txt

@@ -85,7 +85,7 @@ add_custom_command(
   COMMAND ${CMAKE_COMMAND}
   ARGS
     -E
-    copy_directory
+    copy_if_different
     ${CMAKE_CURRENT_SOURCE_DIR}/CrashReporter.nib
     ${CMAKE_CURRENT_BINARY_DIR}/${CMAKE_CFG_INTDIR}/mac-crash-logger.app/Contents/Resources/CrashReporter.nib
   )