Missing HAIKU_TOP causes build problems

[axeld]

Building Haiku no longer works when the build was not started from the generated directory. I usually configure the main build from haiku's top directory, which results in a generated/ directory -- I could then run the builds for this target from anywhere. In this case HAIKU_TOP would be ..

This no longer works, as the current working directory is changed during the build, which results in an error when PackageWriterImpl.cpp tries to resolve HAIKU_BUILD_SYSTEM_DATA_DIRECTORY, as the path is then relative.

[kallisti5]

Error seen when this occurs:

BuildHaikuPackage1 generated/objects/haiku/x86/packaging/packages/haiku.hpkg 
haiku.hpkg: Removing and re-creating package contents dir ...
haiku.hpkg: Collecting package contents ...
haiku.hpkg: mimeset'ing package contents ...
haiku.hpkg: Creating the package ...
unable to find system data path: No such file or directory!

[bonefish]

Fixed in hrev46116.