Done:

apt-get install libc6-* zlib1g:armhf libssl1.0.0:armhf libexpat1:armhf libbz2-1.0:armhf libffi-dev:armhf libncurses5:armhf

ln -s /usr/lib/arm-linux-gnueabihf/libffi.so.6 /usr/lib/arm-linux-gnueabihf/libffi.so.5

Now have:

root@nanopineo2:~/pypy3-v5.5.0-linux-armhf-raspbian/bin# gdb ./pypy3
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "aarch64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
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Reading symbols from ./pypy3...(no debugging symbols found)...done.
(gdb) run
Starting program: /root/pypy3-v5.5.0-linux-armhf-raspbian/bin/pypy3

Program received signal SIGSEGV, Segmentation fault.
0xf77cadde in ?? () from /lib/ld-linux-armhf.so.3
(gdb)