Mac OSX: i386 vs x86_64 in setup_sdk?

[Jeff Earickson]

Why does setup_sdk in .jhbuildrc-custom specify i386 and not x86_64 for
Macs?  I run on a modern Mac (3.3 GHz Intel Core i3, Mac OSX 10.9.2).
"uname -m" says x86_64, but "arch" says "i386"; I would guess that the
setup_sdk line specifies what "arch" is set to for the build, right?  I
want 64 bits if I can get it.

How do I start fresh on a rebuild of everything, gtk and gnucash?  "jhbuild
clean"?  Or if I fiddle with setup_sdk, do I have to go back to the
beginning of "sh gtk-osx-build-setup.sh; jhbuild build python; jhbuild
bootstrap"?

Jeff Earickson