Cross-toolchains for the ARM hard-float ABI

[ibiris 24feb2012] Moving to backlog to determine what still needs to be done with this one

Deliverables:

1. Acquire/package up toolchain which will build Debian/Ubuntu to run on ARM v7, Thumb 2, hard float ABI
    a. Push our desired triplet upstream (arm-linux-gnueabihf)
    b. Investigate the cost (etc.) of runtime linker checking for correctness
    c. Work with LSB and other interested people to make sure we keep binary compatibility
2. Verify the toolchain:
    a. Make sure it is actually producing armhf binaries - nobody has actually verified this yet
    b. Report bugs/feedback for the toolchain team based on testing and benchmarks
3. Support for other teams interested in the hf ABI as/when desired? (Android / other Linux distros / ChromeOS?)

===
Work items (11.10):
[steve-mcintyre] Add support into the runtime linker to check on attributes - make sure we're using hf ABI: DONE
[steve-mcintyre] Benchmark cost of the runtime linker doing those checks: DONE

Work items (11.12):
[steve-mcintyre] Help with getting the armhf cross-toolchain into Debian/Ubuntu: POSTPONED
[steve-mcintyre] Verify that we're actually producing hf ABI binaries: DONE
[steve-mcintyre] Investigate feasibility/value of changing the name of the runtime linker for armhf: DONE
[steve-mcintyre] Investigate best methods to support non-multiarch users: DONE
[steve-mcintyre] Create a <email address hidden> mailing list: DONE

Work items (12.01):
[steve-mcintyre] Push triplet to upstream gcc and get it accepted: TODO
[steve-mcintyre] Document exactly what "armhf" means in terms of the AAPCS, triplet etc.: INPROGRESS