regression on -current with rust-1.70.0

rust doesn't build anymore on slackware64 -current:

Code:Traceback (most recent call last):
File "/tmp/rustc-1.70.0-src/./x.py", line 29, in <module>
bootstrap.main()
File "/tmp/rustc-1.70.0-src/src/bootstrap/bootstrap.py", line 950, in main
bootstrap(args)
File "/tmp/rustc-1.70.0-src/src/bootstrap/bootstrap.py", line 914, in bootstrap
build.download_toolchain()
File "/tmp/rustc-1.70.0-src/src/bootstrap/bootstrap.py", line 439, in download_toolchain
self._download_component_helper(filename, "rustc", tarball_suffix)
File "/tmp/rustc-1.70.0-src/src/bootstrap/bootstrap.py", line 475, in _download_component_helper
unpack(tarball, tarball_suffix, self.bin_root(), match=pattern, verbose=self.verbose)
File "/tmp/rustc-1.70.0-src/src/bootstrap/bootstrap.py", line 132, in unpack
for member in tar.getnames():
File "/usr/lib64/python3.9/tarfile.py", line 1981, in getnames
return [tarinfo.name for tarinfo in self.getmembers()]
File "/usr/lib64/python3.9/tarfile.py", line 1973, in getmembers
self._load() # all members, we first have to
File "/usr/lib64/python3.9/tarfile.py", line 2668, in _load
tarinfo = self.next()
File "/usr/lib64/python3.9/tarfile.py", line 2573, in next
self.fileobj.seek(self.offset - 1)
File "/usr/lib64/python3.9/lzma.py", line 261, in seek
return self._buffer.seek(offset, whence)
File "/usr/lib64/python3.9/_compression.py", line 143, in seek
data = self.read(min(io.DEFAULT_BUFFER_SIZE, offset))
File "/usr/lib64/python3.9/_compression.py", line 99, in read
raise EOFError("Compressed file ended before the "
EOFError: Compressed file ended before the end-of-stream marker was reachedCode:-rw-r--r-- 1 root root 6380780 avril 20 16:13 cargo-1.69.0-x86_64-unknown-linux-gnu.tar.xz
-rw-r--r-- 1 500 500 261 nov. 19 2020 link_libffi.diff.gz
-rw-r--r-- 1 root root 19922944 sept. 2 05:37 rustc-1.69.0-x86_64-unknown-linux-gnu.tar.xz
-rw-r--r-- 1 500 500 145507120 juin 1 20:51 rustc-1.70.0-src.tar.lz
-rwxr-xr-x 1 500 500 9913 juil. 13 19:10 rust.SlackBuild*
-rw-r--r-- 1 root root 28553440 avril 20 16:15 rust-std-1.69.0-x86_64-unknown-linux-gnu.tar.xz
-rw-r--r-- 1 500 500 1670 juin 12 20:51 rust.url
-rw-r--r-- 1 500 500 910 fivr. 27 2018 slack-desc