[Bug bootstrap/68540] 6.0 build process broken on Linux Mint, potential include ordering problem

[martin@mpa-garching.mpg.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68540

--- Comment #8 from Martin Reinecke <martin@mpa-garching.mpg.de> ---
I confirm that I can build again when provoding the ISL 0.15 sources withon the
gcc/ directory.

In order to save others some head-scratching, would it be possible to update
the ISL version check in the configuration machinery so that it gives a clear
error when encountering an ISL version that is too old?