Improve support for porters - SDK/sysroot

[hrw, 201X-XX-XX] This blueprint is blocked because it require eglibc 2.17. Linaro cross toolchain is using eglibc 2.16.
[fboudra, 2013-02-01] Toolchain is updated to eglibc for 13.02 cycle. Added a dependency on their blueprint.
[asac, 2013-02-06]: my undersatnding is that this is about the cross SDK; cross-SDK with linaro binary toolchain is probably blocked by eglibc2.17 not being in the toolchain, but the rest of the cross SDK story should be doable still..

[hrw, 2013.02.18] OE based SDK works fine and is used for HipHopVM porting. Did few updates due to requests from Owen. Also will be used by Leif to debug TBB test failures. LAMP/SDK sysroot for TCWG cross compiler is slowly in progress - I have image which cover both but it has lot of binaries which we will not use anyway.

[hrw 2013.02.20] First draft of documentation: https://wiki.linaro.org/MarcinJuszkiewicz/Sandbox/ARMv8-use-TCWG-crosscompiler-with-OE-sysroot

Meta:
Headline: OpenEmbedded based SDK is now able to build HipHopVM
Acceptance: SDK is capable of building HipHopVM
Roadmap id: CARD-327

Work items:
create LAMP sysroot for TCWG cross compiler (kind of meta-toolchain without toolchain): DONE
check OE SDK for LAMP: DONE
document how to build something with TCWG cross: DONE
document how to add it into existing image: DONE
merge LAMP and SDK images into one: DONE
switch Jenkins to not build SDK image: DONE