Build failure in scratch on editor backup files

When working with a file in scratch I encounter variations of this error:

$ ./ns3 run ...
...
-- Processing src/wimax
CMake Error at scratch/CMakeLists.txt:14 (file):
  file failed to open for reading (No such file or directory):

    /(path elided)/scratch/.#tird.cc
Call Stack (most recent call first):
  scratch/CMakeLists.txt:67 (create_scratch)


-- ---- Summary of optional ns-3 features:
...
-- Configuring incomplete, errors occurred!
See also "/Users/barnes26/Code/netsim/ns3/repos/ns-3-dev/cmake-cache/CMakeFiles/CMakeOutput.log".
See also "/Users/barnes26/Code/netsim/ns3/repos/ns-3-dev/cmake-cache/CMakeFiles/CMakeError.log".
FAILED: build.ninja 
/opt/local/bin/cmake --regenerate-during-build -S/Users/barnes26/Code/netsim/ns3/repos/ns-3-dev -B/Users/barnes26/Code/netsim/ns3/repos/ns-3-dev/cmake-cache
ninja: error: rebuilding 'build.ninja': subcommand failed

The important bit is file failed to open for reading (No such file or directory):, followed by the path to an editor temporary file (in this case from emacs, holding unsaved changes).

Probably should restrict the build to non-hidden files ending in `.cc'