Cannot build ports on fresh 10.0

I installed a new VM with 10.0 today from this .iso:

ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/ISO-IMAGES/amd64/10.0/FreeBSD-10.0-CURRENT-amd64-20130601-r251213-release.iso

And I'm behind a firewall and I'm not sure I can use pkg(1); my one attempt
failed:

# pkg install m4
Updating repository catalogue
Repository catalogue is up-to-date, no need to fetch fresh copy
pkg: Package 'm4' was not found in the repositories

So I'm building from source.  But the configure step of various ports fails
like so:

checking whether make sets $(MAKE)... yes
checking build system type... Invalid configuration
`amd64-portbld-freebsd10.0': machine `amd64-portbld' not recognized
configure: error: /bin/sh libltdl/config/config.sub
amd64-portbld-freebsd10.0 failed
===>  Script "configure" failed unexpectedly.
Please report the problem to autotools_at_FreeBSD.org [maintainer] and attach
the "/usr/ports/devel/libtool/work/libtool-2.4.2/config.log" including the
output of the failure of your make command. Also, it might be a good idea to
provide an overview of all packages installed on your system (e.g. a
/usr/local/sbin/pkg-static info -g -Ea).
*** Error code 1

Any ideas what could be wrong?  It's a fresh install with default options,
so it seems hard to believe I managed to screw something up already.
Posting on -current since this happens to many of the ports when I try to
build them.

Thanks,
matthew