[igraph] ./configure won't detect GMP

[Szabolcs Horvát]

Dear All,

I'm compiling igraph on OS X 10.10.5 using the system compiler.

I'm trying to use GMP 6.0.0 from https://gmplib.org/, which I
installed into $HOME/local.  I configure igraph like this:

export CFLAGS=-I$HOME/local/include
export LDFLAGS=-L$HOME/local/lib
./configure --prefix=$HOME/local

The configure script fails to detect GMP.  How can I get it to succeed?

Notes: It does detect MacPorts's GMP if I try to use it.  It's also
version 6.0.0.  If I remove the part of the configure script that
detects GMP to trick it into thinking that it's present, igraph does
compile correctly, and it does work correctly (including functions
that use GMP).

I don't know anything about autoconf and don't understand how it tries
to detect GMP ...

Am I doing something wrong or is the GMP detection buggy?

Szabolcs