The default configuration for w3m places "gcc" in the editor field and $CFLAGS in the mailer field. This is because the configure program has changed but the src_compile function has not been updated for the new configure sequence.
I've noticed that w3m also has an 0.4 version out, so I'm working on updating the ebuild at the same time.
Fixed in w3m-0.4.ebuild, now stable on x86