Please support "any" architecture when building instead of hardcoding an arch

I built a bunch of click packages from lp:ubuntu-*-app branches on my amd64 desktop and run into quite some difficulty with the "architecture" field in the manifest. It seems our compiled apps currently hardcode "armhf" there:

  http://bazaar.launchpad.net/~ubuntu-filemanager-dev/ubuntu-filemanager-app/trunk/view/head:/manifest.json
  http://bazaar.launchpad.net/~ubuntu-terminal-dev/ubuntu-terminal-app/trunk/view/head:/manifest.json

 - When I build a click from that [1], I get a com.ubuntu.filemanager_0.3.212_armhf.click which I can't install into an amd64 schroot/LXC. Also, hardcoding it that way seems ugly/wrong to me.

 - When I simply drop it, click assumes "all" (that's not documented on https://click.readthedocs.org/en/latest/file-format.html#control-area), and I can install it on amd64, but it will not work when installing it on another arch

 - When I change it to ["armhf", "i386", "amd64"] then it'll build com.ubuntu.filemanager_0.3.212_multi.click which I can install on x86 (tests run fine). But that's still wrong as it will still only work for the architecture you build it on.

Thus I think there should be an "architecture": "any" (or similar) for compiled apps which will behave like dpkg does and replace "any" with the build target architecture.

[1] I use these commands for building:
checkout=/tmp/ubuntu-calculator-app
rm -rf /tmp/build /tmp/inst; mkdir /tmp/build; cd /tmp/build
cmake $checkout -DINSTALL_TESTS=off -DCLICK_MODE=on -DBZR_REVNO=$(bzr revno $checkout)
make -j4
make install DESTDIR=/tmp/inst
click build /tmp/inst