c-t-b-ports fails to building glibc for arc-linux-gnu

Package: src:cross-toolchain-base-ports, src:linux, src:glibc
Severity: serious
Tags: sid forky ftbfs

cross-toolchain-base-ports ftbfs in the glibc stage1 target.  I haven't 
figured out what is exactly wrong about it, as it is the only target 
with that kind of build failure.

In file included from ../sysdeps/unix/sysv/linux/bits/errno.h:26,
                  from ../stdlib/errno.h:28,
                  from ../include/errno.h:2,
                  from ../sysdeps/unix/sysdep.h:28,
                  from ../sysdeps/unix/sysv/linux/arc/sysdep.h:24,
                  from ../sysdeps/arc/nptl/tls.h:33,
                  from ../include/link.h:51,
                  from <stdin>:1:
/usr/include/linux/errno.h:1:10: fatal error: asm/errno.h: No such file 
or directory
     1 | #include <asm/errno.h>
       |          ^~~~~~~~~~~~~
compilation terminated.
rm -f 
/build/reproducible-path/cross-toolchain-base-ports-77/glibc-2.43/build-tree/arc-libc/sem_t-align.h.dT

The build still uses gcc-15, glibc now has a new upstream version, and 
the linux headers are provided by the linux source package.

full build log at
https://buildd.debian.org/status/package.php?p=cross-toolchain-base-ports

Debian doesn't have an arc port, so one option possibly is to drop the 
arc target as well.