d/p/test-backtrace.patch: update to fix FTFBS with glibc 2.33 and later

With glibc 2.33 (in Ubuntu already) this fails. The upstream version would work on more common architectures.

Full string of the backtrace is:

(gdb) printf "%s\n", str_c(bt)
/build/dovecot-bRiyOq/dovecot-2.3.13+dfsg1/src/lib/test-lib(+0x83729) [0x5555555d7729]
-> /build/dovecot-bRiyOq/dovecot-2.3.13+dfsg1/src/lib/test-lib(test_backtrace+0x90) [0x55555558a9e0]
-> /build/dovecot-bRiyOq/dovecot-2.3.13+dfsg1/src/lib/test-lib(+0x7e74e) [0x5555555d274e]
-> /build/dovecot-bRiyOq/dovecot-2.3.13+dfsg1/src/lib/test-lib(test_run_named_with_fatals+0x7d) [0x5555555d530d]
-> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xd5) [0x7ffff7dfa565]
-> /build/dovecot-bRiyOq/dovecot-2.3.13+dfsg1/src/lib/test-lib(_start+0x2e) [0x5555555852ee]

It comes down to glibc 2.33 changing behavior in regard to dovecots backtrace_append_libc of src/lib/backtrace-string.c. We can't report this upstream as it only affects the Debian Delta.

Comparing what would be in the backtrace on various architectures and with odl and new glibc it seems "test_backtrace" is more reliable. Hence let us adapt the fix for that.