Problem setting runpath

I'm on Solaris 10 (Intel) using gcc. I'd like to add /usr/local/lib to 
the built-in runpath. I've tried

1. setting LD_RUN_PATH=/usr/local/lib before running configure (also 
tried adding this to the command line for configure).

2. Adding LDFLAGS='-Wl,--runpath,/usr/local/lib' to the configure 
command line.

The upshot is that /usr/local/lib doesn't get included in the runpath, 
and I have to set LD_LIBRARY_PATH to get things to work. I'd rather not 
do that because this will be used in an environment where users set lots 
of different LD_LIBRARY_PATH in their shell startup files.

I know I can use crle to add /usr/local/lib systemwide, but that makes 
me nervous, and I'd rather get runpath to work if I can.

How can I tell configure to add /usr/local/lib to runpath, and have that 
built into the executables?

Thanks

Joe