Use Autoconf to find path to ldconfig.

diff --git a/configure.in b/configure.in
index bdc9bed..ea723d3 100644
--- a/configure.in
+++ b/configure.in
@@ -74,6 +74,7 @@
 AC_PROG_INSTALL
 AC_PROG_LN_S
 AC_CHECK_PROG(C2MAN,c2man,c2man,true)
+AC_PATH_PROG(LDCONFIG, ldconfig, false, /sbin:/usr/sbin:$PATH)
 
 dnl **** Check for some libraries ****