cat: catch strace injection of 2nd+ splice

[oech3]

Please merge #12651 at 1st.
This catches 2nd+ strace injection for splice (preliminary for GnuTests: cat/splice.sh). We don't pass it yet as read/write errors are not separated yet.

$ strace -o /dev/null -e inject=splice:error=EINTR:when=3 target/debug/cat /dev/zero
cat: /dev/zero: Interrupted system call

related with #12605 , but not 100% fix.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/pipe-f is now passing!
Note: The gnu test tests/misc/write-errors was skipped on 'main' but is now failing.
Skip an intermittent issue tests/pr/bounded-memory (was skipped on 'main', now failing)