how to override precious variables for subdirs

[Chris Frey]

Hi,

I have a software package (Barry) that contains a number of subdirectories,
using the AC_CONFIG_SUBDIRS feature.

These subdirectories depend on the library that is built in the main tree.

Normally, I just export PKG_CONFIG_PATH to include the main tree, so
that the subdirectories' configure scripts can find the library.

Recently, PKG_CONFIG_PATH has become precious.  This means that when the
subdirectory configures are run, then PKG_CONFIG_PATH is set on the
command line, if it was set for the main directory.

So far, I have been unable to find any way to override this precious state
for subdirectories.

Is there a way to override this?  Is there a better way to achieve the
same ends?

Thanks!
- Chris