[Interest] QWE: ${build.dir}/src/toolchain/BUILD.gn not being created at first configure run

[René J. V. Bertin]

Hi,

Building QWE 5.9.3 on Linux I run into an issue that others have also found but 
apparently only when cross-compiling: src/toolchain/BUILD.gn isn't created at 
first under the build dir:

https://www.google.com/search?q=webengine+%22ERROR+at+%2F%2FBUILD.gn%3A74%3A1%3A+Can%27t+load+input+file.
%22&oq=webengine+%22ERROR+at+%2F%2FBUILD.gn%3A74%3A1%3A+Can%27t+load+input+file.
%22

I'm not cross-compiling, I'm simply doing an out-of-tree build.

Why does this happen? The only leads I found were "install gperf flex and bison" 
(I already had all 3) and "just run the configure step once more". That works, 
but is a bit kludgy and not feasible for packaging scripts and CI set-ups.

FOrtunately the contents of the file are straightforward and trivial to get right 
starting with a template *before* running the initial configure, but that has 
side-effects too. It gives a 2nd build during the configure step: first 330 files 
corresponding to building Ninja (I think), then 639 more files it didn't build 
before.

Does anyone have a real fix?

Thanks,
René