php70 @7.0.9: PHAR build fails on Mac OS X 10.5.8

[land.apfel@…]

Building php70+universal (ppc + ppc64) fails on Mac OS X 10.5.8 with:

Generating phar.php
Generating phar.phar
PEAR package PHP_Archive not installed: generated phar will require PHP's phar extension be enabled.
make: *** [ext/phar/phar.phar] Illegal instruction
make: *** Waiting for unfinished jobs....
make: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_php/php70/work/php-7.0.9'
Command failed:  cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_lang_php/php70/work/php-7.0.9" && /usr/bin/make -j2 -w all
Exit code: 2
Error: org.macports.build for port php70 returned: command execution failed

(full main.log​ attached)

As a workaround, removing --enable-phar from configure.args has worked for me.

But of course it would be better to fix the real problem. I'd be happy to help figuring out the real problem.