gcc-build fails with isl error when trying to build latest gcc on Debian 13/trixie

[N7DR]

While waiting for issue #23 to be fixed, I tried the rust version, gcc-builder (on Debian 13/trixie). I believe that I followed the directions correctly.

I executed:
gcc-builder --latest --prefix $HOME/gcc --jobs $(nproc) --build-dir /tmp/gcc-build

and, after everything was downloaded, received:

checking for isl 0.15 or later... no
required isl version is 0.15 or later
configure: error: Unable to find a usable isl. See config.log for details.

I don't know what isl is, or where to find it. apt doesn't seem to find it (there is no Debian isl package), so I think I'm stuck.

[N7DR]

Looking around the internet, I saw that perhaps isl is provided by the libisl package. But that is already installed (as is libisl-dev). The current version of libisl installed on trixie from the debian stable repository is 0.27 (therefore > 0.15).