Compilation of Ardour3 fails: cannot find libsndfile

[Tommy Bongaerts <tommy.bongaerts@drumscum.be>]

Hello list,

I'm trying to install Ardour3 on my Debian Lenny box, but configuring
fails because it cannot find the sndfile 1.8 library:

tommy@mordor:~/src/svn/ardour/3.0$ scons PREFIX=/opt
scons: Reading SConscript files ...
Checking for pkg-config version >= 0.8.0... yes
Checking for aubio... yes
Checking for ogg... yes
Checking for gthread-2.0... yes
Checking for lrdf... yes
Checking for libgnomecanvas-2.0... yes
Checking for gtk+-2.0... yes
Checking for jack... yes
Checking for flac... yes
Checking for sndfile... no
sndfile >= 1.0.18 not found.
You do not have the necessary dependencies required to build ardour
Please consult http://ardour.org/building for more information

I have however installed libsndfile 1.0.18 from source with
--prefix=/opt. I also ran ldconfig to update my libraries cache.
/opt/lib is in my ld.so.conf, so scons should be able to locate the
correct libraries, no? 

tommy@mordor:~/src/svn/ardour/3.0$ cat /etc/ld.so.conf
include /etc/ld.so.conf.d/*.conf
/opt/lib

Anyone knows what could be wrong here?

-- 
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but World War IV will be fought with sticks and stones.
	~ Albert Einstein