After looking/comparing at the output of `./configure` for our i386 and amd64 builds against that of Debian's i386 build, our i386 build was the only one of the three to include `checking whether to force non-PIC code in shared modules... yes` (the other two were `no`).
Debian includes `--with-pic`, and we do not.
Looking at the upstream PHP code for this configure check (313a56add0/configure.ac (L241-L256)), this makes total sense, and explains why i386 is the only architecture we see this issue on:
```m4
dnl Disable PIC mode by default where it is known to be safe to do so, to avoid
dnl the performance hit from the lost register.
AC_MSG_CHECKING([whether to force non-PIC code in shared modules])
case $host_alias in
i?86-*-linux*|i?86-*-freebsd*)
if test "${with_pic+set}" != "set" || test "$with_pic" = "no"; then
with_pic=no
AC_MSG_RESULT(yes)
else
AC_MSG_RESULT(no)
fi
;;
*)
AC_MSG_RESULT(no)
;;
esac
```
This was probably already implied by our `CFLAGS` (and the compiler) on Alpine, but I figured it doesn't hurt to be explicit / consistent.
See https://github.com/docker-library/php/pull/1028#issuecomment-649763859 for details -- Someone™ needs to dig into the `pdo_mysql` build issue for this to return:
> `PHP Warning: PHP Startup: Unable to load dynamic library 'pdo_mysql.so' (tried: /usr/local/lib/php/extensions/no-debug-zts-20190128/pdo_mysql.so (Error relocating /usr/local/lib/php/extensions/no-debug-zts-20190128/pdo_mysql.so: _tsrm_ls_cache: initial-exec TLS resolves to dynamic definition in /usr/local/lib/php/extensions/no-debug-zts-20190128/pdo_mysql.so)`
