[Mono-list] mono 0.23 with gc6.1 building help

[Eric Rae]

i'm trying to install mono 0.23 with gc6.1.

After downloading and untaring mono_0.23.tar.gz and gc6.1.tar.gz....
I do the following

/usr/mono/gc6.1/> ./configure
/usr/mono/gc6.1/> make
/usr/mono/gc6.1/> make install
.... installs libs to /usr/local/lib ....
.... /usr/local/lib into /etc/ld.so.conf
/usr/mono/gc6.1/> ldconfig
/usr/mono/gc6.1/> ln -s /usr/local/include/gc /usr/mono/gc6.1/include

/usr/mono/mono-0.23/> ./configure
.... configure returns ... GC: boehm ....
/usr/mono/mono-0.23/> make
.... make returns following error ....

../io-layer/.libs/libwapi.al(timed-thread.lo): In function
 `timed_thread_start_routine':
/usr/mono/mono-0.23/mono/io-layer/timed-thread.c:88: undefined reference
to `GC_pthread_detach'
../io-layer/.libs/libwapi.al(timed-thread.lo): In function
`_wapi_timed_thread_create':
/usr/mono/mono-0.23/mono/io-layer/timed-thread.c:124: undefined
reference to `GC_pthread_create'
collect2: ld returned 1 exit status
make[3]: *** [pedump] Error 1
make[3]: Leaving directory `/usr/mono/mono-0.23/mono/metadata'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/usr/mono/mono-0.23/mono'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/mono/mono-0.23'
make: *** [all-recursive-am] Error 2
/usr/mono/mono-0.23>

I don't know what to fix... how do I build mono-0.23 with gc6.1 support.
(if I install mono without gc6.1, mono builds and installs fine.)

Thanks for your help / advise.