depends: create a hostid and buildid and add option for salts
These add very simple sanity checks to ensure that the build/host toolchains
have not changed since the last run. If they have, all ids will change and
packages will be rebuilt.
For more complicated usage (like parsing dpkg), HOST_ID_SALT/BUILD_ID_SALT may
be used to introduce arbitrary data to the ids.
Documentation more readable when viewed on Github.
Some extra changes by @laanwj:
- Make README.usage the default README. This is more convenient from a
user perspective. Link to other documentation in this default README
- Add list of popular targets for cross compilation, change default to
Win64 instead of Win32