CEF 76+ switched to a new helper bundling scheme. Until I find time to
address that (looks easy -- this just isn't a high priority for me any
longer), we need to stick with versions prior to that, so downgraded
back to version 75.1.4+g4210896+chromium-75.0.3770.100.

Issue https://bitbucket.org/chromiumembedded/cef/issues/2737/macos-76-requires-multiple-helper-app
has details.

With the ommission of the C++ header, some src references point to
"<scratch space>", which isn't valid.