[tlbuild] trunk is broken

[Karl Berry]

      but with these 2 changes, if someone is not using the Build script but
      running configure manually, he is now required to use absolute path.

Thanks for working on this, but no one running configure manually will
ever think of doing that.  It's unprecedented.  So, I have to 
say that those changes should be reverted.  Sorry.

If eliminating $(install_makeargs) solves the problem on Solaris, I'm ok
with that.  It seems that is a mistake (these days) anyway.

Ultimately zziplib et al. need to be fixed.  If you feel like working on
that, I'm sure Taco will accept the changes.

(Other luatex-related annoyances I've noticed are that some of the
libraries get rebuilt every time, and consequently the luatex binary
also, even at make install.  Oh well ...)

karl