Although I was root in the container, the GCC4TI build does not require either root access or a well-defined source directory. Easy installiation of build dependencies coherent with the rest of the distro packages does, of course, but you write that don't have root access...
Per the above, the build succeeds (twice) in a clean environment which has all of the build deps in versions coherent with the other packages in the distro, so maybe your environment has some oddity in e.g. the environment variables (PATH, LD_LIBRARY_PATH, INCLUDE_PATH, LIBRARY_PATH, PKG_CONFIG_PATH, etc.), missing build deps, different deps versions, etc.
I suppose that I can produce and upload an installation prefix for you... let me do that.
[EDIT:
https://tiplanet.org/beta/gcc4ti-git-next-opensuse-leap-15.3.tar.bz2 . That's the result of the script I posted above, and edited. The build prefix was /data/prefix , but it shouldn't matter.]
My "ancient version" note was based on the fact that the commands I listed above pulled in e.g. GCC 7 (now over 4 years old, considering that GCC has a yearly release cycle with a new version released in the Northern hemisphere spring, and that the current latest series is 11) and Perl 5.26