Postpone the evaluation of macro to installation

[Liguo Song <Liguo Song vanderbilt edu>]

Hi, folks,

I am trying to build a package for a ruby wrapper. The files will be installed 
to directories depend on the version of the ruby package and the current host 
OS, which is the way ruby wants. For example, directory would be 
/usr/lib/ruby/1.8/i686-linux-gnu/ for ruby-1.8 on RH8.0 and i686, but it will be 
/usr/lib/ruby/1.6/i386-linux/ for ruby-1.6 on RH7.0 and i386.

I figure out the way to determine these directories by invoking ruby and defined 
the results as macros. But all these macros are evaluated at the compile time. 
So, the directories will not work if the ruby versions are different on the 
building host and the installing host.

I can put my files into a directory independent of the ruby version, and put 
links to them from the right places in the post install phase. But, the macros 
are all evaluated when I compile the src package, so the direcotries won't work 
for the installing host.

My question is whether there is a way to postpone the evaluation of the macros 
to the installation time? If so, how to achieve this?

Thanks in advance for any input.


Liguo (Leo)