Did you get this working?
Yes.
1) I have used crosstools
http://kegel.com/crosstool/crosstool-0.43/doc/crosstool-howto.html on ubuntu to build the compiler. I was able to build a statically linked binary "hello world" which could run on ds. I didn't go further.
2) With a chrooted debian you can make something like apt-get install build-essentials and then compile directly on the ds. I use this if I need something what is not in debian or ipkg.
I got the GCC compiler installed through the Toolchains but in my case './configure' and 'make' does not get the PHP using the extension libxml.
Is your problem the compiler itself or the ./configure, make process (e.g. missing libraries etc...) ? But then again I didn't go this direction so I'm afraid but probably I will be of no use to you...
Do you have a step-by-step for getting php extensions to work on the DS-106??
No.
I have simply installed IPKG and then php-fcgi with ipkg install. This version is compiled with this parameters:
'./configure' '--build=i386-pc-linux-gnu' '--host=powerpc-603e-linux' '--target=powerpc-603e-linux' '--prefix=/opt' '--with-config-file-scan-dir=/opt/etc/php.d' '--with-layout=GNU' '--disable-static' '--enable-dba=shared' '--with-inifile' '--with-flatfile' '--enable-dom=shared' '--enable-exif=shared' '--enable-ftp=shared' '--enable-pdo=shared' '--enable-shmop=shared' '--enable-sockets=shared' '--enable-sysvmsg=shared' '--enable-sysvshm=shared' '--enable-sysvsem=shared' '--enable-xml=shared' '--enable-xmlreader=shared' '--with-bz2=shared,/home/slug/optware/ds101g/staging/opt' '--with-db4=/home/slug/optware/ds101g/staging/opt' '--with-dom=shared,/home/slug/optware/ds101g/staging/opt' '--with-gdbm=/home/slug/optware/ds101g/staging/opt' '--with-openssl=shared,/home/slug/optware/ds101g/staging/opt' '--with-sqlite=shared' '--with-pdo-sqlite=shared' '--with-xsl=shared,/home/slug/optware/ds101g/staging/opt' '--with-zlib=shared,/home/slug/optware/ds101g/staging/opt'
'--with-libxml-dir=/home/slug/optware/ds101g/staging/opt''--with-jpeg-dir=/home/slug/optware/ds101g/staging/opt' '--with-png-dir=/home/slug/optware/ds101g/staging/opt' '--with-freetype-dir=/home/slug/optware/ds101g/staging/opt' '--with-zlib-dir=/home/slug/optware/ds101g/staging/opt' '--with-gettext=/home/slug/optware/ds101g/staging/opt' '--enable-maintainer-zts' '--with-pcre-regex=/home/slug/optware/ds101g/staging/opt' '--with-regex=php' '--without-iconv' '--without-pear' '--enable-spl' '--enable-memory-limit' '--disable-cli' '--enable-cgi' '--enable-fastcgi' '--enable-force-cgi-redirect'
That solved my problems with php so I didn't do anything more.