Replace build system vars [PRIVATE_]SYSTEM_LIBS by rules

... HaikuImageGetSystemLibs and HaikuImageGetPrivateSystemLibs.
Remove SYSTEM_LIBS*_ALIASES build variables
PreprocessPackageInfo: define macro for secondary architecture
Support building libpackage-add-on-libsolv.so for secondary arch
libtracker: VirtualDirectoryManager::_RemoveDirectory(): typo

Should have caused infinite recursion when the directory still had
children.
Add node_ref::operator <

Moved from VirtualDirectoryManager. Defining the operator static doesn't
work with gcc 4 and it's useful to have globally available anyway.
Support building most system libraries for secondary arch

Also adjust the HaikuImageGet[Private]SystemLibs rules to support to
return the library targets matching the current architecture.
Add package definition HaikuSecondaryBootstrap

A haiku_<arch>.hpkg package is produced for each secondary architecture.
AddHaikuImagePackages/IsHaikuImagePackageAdded: 2ndary arch fix

For the secondary architecture the same specified package name means a
different package, so we need to use the mapped name IsPackageAvailable
returns.
package info haiku_secondary: fix description

Using the C preprocessor doesn't work particularly well. The
replacements are rather unhandy.
HaikuDevel: a few simplifications
Add HaikuDevelSecondary package definition

It defines the haiku devel package for a secondary architecture
(haiku_<arch>_devel.hpkg).
Add secondary arch haiku [devel] packages to image
Add the missing secondary arch bootstrap packages

The Haiku bootstrap image is now built with (hopefully) all required
primary and secondary architecture packages. The runtime loader is still
resisting our wish to run secondary architecture programs, though.