Precompiled header is broken with anything but C++ (C, Objective-C, Objective-C++)

Attempting to use a precompiled header with any language but C++ will fail. In one instance this resulted in a massive amount of error messages as if it was trying to send a binary file through the compiler, though in my test case it just fails immediately saying 'invalid pch'.

"In file included from <command-line>:0:
/path/to/src/build/500-64-debug/MyProject:1: error: stray ‘\317’ in program"

I've attached a test case - rename the pchbug.cpp file (it's a polyglot) to pchbug.c, pchbug.m, or pchbug.mm and observe that "warning: /path/to/pchbug.gch: not for GNU <language name>" is output and the project fails to build.

I understand the property is cpp.precompiledHeader but surely we want it to work with all four C-family languages?