[yocto] Setup repository for ADT installer

[Lu, Lianhao]

Hi Beth and Jessica,

Here is a summary of how I set up the IPK repo for ADT installer on my local machine. Currently, there are 10 combinations (based on the following 2 variables in conf/local.conf) needs to be built for setting up the ADT installer repo.

MACHINE: qemux86, qemuarm, qemuppc, qemumips, qemux86-64
SDKMACHINE: i586, x86_64

NOTE: Please make sure the PACKAGE_CLASSES has the value of "package_ipk".

First, we need to generate the kernel/target rootfs images, as well as the ipk files and the repository index files. Then we need to make those generated files available through HTTP protocol. 

1. Generate kernel/target rootfs images, as well as the ipk files and repository index files. 
For each of the combinations:
1.1) bitbake poky-image-sdk   
1.2) bitbake meta-toolchain-sdk

Step 1.2) will generate more ipk files than the ADT installer needs, and also create the meta-toolchain-sdk-XXX.tar.gz under deploy/sdk which is not used by the ADT installer. We may split step 1.2) into the following commands if we just want to generate the files only for ADT installer.

bitbake task-sdk-host    								#generate ipk files for host utils
bitbake task-cross-canadian-<TRNASLATED_TARGET_ARCH>  	#generate ipk files for cross-canadian tool chain
bitbake package-index									#generate the repository index files

The <TRNASLATED_TARGET_ARCH> is based on the MACHINE configuration in conf/local.conf
MACHINE    <TRANSLATED_TARGET_ARCH>
qemux86     i586
qemuarm     arm
qemuppc     powerpc
qemumips    mips
qemux86-64  x86-64

2. Setup a web server for adt-installer to access the files through http protocol
The ADT-installer needs to access the following directories through http, so we need to set up a web server for user to access.

${BUILD_DIR}/tmp/deploy/ipk
${BUILD_DIR}/tmp/deploy/images


b.t.w. I think the final directory layout of the repo	will influence adt installer, because currently the repo's top level layout is hard coded in the installer. Here are something we think need to consider (Liping, pls add more information here):
- yocto release version
- file name conventions for the built kernel

Best Regards,
-Lianhao Lu