Binary toolchain questions summary

[Michael Hope]

Here's my summary from Monday's meeting on the harder parts of binary
toolchains.

Using a 4.6 compiler against a 4.5 based sysroot such as Natty:
 * libgcc and libstdc++ are part of the compiler
 * The compiler expects features that are in the corresponding runtime
 * You can't reliably run or validate against an earlier runtime

The solution is to upgrade the runtime on the sysroot to 4.6.  4.6 is
backwards compatible.  Ubuntu did this with Maverick and it caused no
problems, although problems such as Debian #622783 have been seen.

Multiarch:
 * The Ubuntu multiarch patch should work with a sysroot
 * Multiarch and multilib should work together

Multilib:
 * The current ARM multilib rules are old and not very relevant
 * Multilib means you need multiple sysroots as well
 * Skip multilib for the first release

Other:
 * Anything we support in cross we should support native first
 * Check that we don't have to directly supply the source that goes
with the binary sysroot

-- Michael