Add note to INSTALL explaining how to use libraries from /usr/local.

Several users have had trouble building PSPP with self-built GSL, etc.
that were installed to /usr/local.  Explain how to do it here to be
more friendly to Unix novices.

Thanks to Jim Orr for making me realize that this was important.

diff --git a/INSTALL b/INSTALL
index c07faa27841a284c8231fded9edd970e8755c0bd..ea43342eef7223bce3b2fcb76d5ba817166bf2fd 100644 (file)
--- a/INSTALL
+++ b/INSTALL
@@ -108,6 +108,19 @@ release.
   1. `cd' to the directory containing the package's source code and type
      `./configure' to configure the package for your system.
 
+     You may invoke `configure' with --help to see what options are
+     available.  The most common of these are listed under "Optional
+     Features", below.
+
+     If you installed some of the libraries that PSPP uses in a
+     non-standard location (on many systems, anywhere other than
+     /usr), you may need to provide some special flags to `configure'
+     to tell it where to find them.  For example, on GNU/Linux, if you
+     installed some libraries in /usr/local, then you need to invoke
+     it with at least the following options:
+
+       ./configure LDFLAGS='-L/usr/local/lib -Wl,-rpath,/usr/local/lib' CPPFLAGS='-I/usr/local/include'
+
      Running `configure' takes awhile.  While running, it prints some
      messages telling which features it is checking for.