1446030 - Try a little harder to make sure the clang we're going to use for bindgen works

Status: NEW

(Firefox Build System :: General, enhancement)

Description

[(not currently active) Ted Mielczarek]

I'm still working on reviving my WSL patch series, and I got it to the point where it ran stylo's bindgen build script and that failed on me with a huge backtrace + a pile of warnings from clang. Scrolling all the way up to the top showed me:
 4:16.12 /mnt/c/Program Files (x86)/Microsoft Visual Studio/2017/Community/VC/Tools/MSVC/14.13.26128/include/yvals.h:168:5: error: STL1000: Unexpected compiler version, expected Clang 5.

The line in yvals.h is literally `#if __clang_major__ < 5`, and the clang I had installed was 3.9 because I hadn't touched my WSL build env in a while.

It would be nice if we could figure this out in configure and print a more useful error. I'm not sure what the right thing to do here is. yvals.h seems to be included by all the <c*> C++ headers in Microsoft's CRT, so simply feeding the bindgen clang something like `#include <cstdio>` would probably surface this particular error.