scons conf.CheckLib() does not find libcppunit even though it is there and working

[Jan]

On our system, building with the vanilla SConstruct file fails because scons does not find the cppunit library:

jan@nepomuk:/data/jan/clean/openwns-sdk$ ./playground.py install
Executing: scons dbg --warn=no-missing-sconscript -j 8 default
scons: Reading SConscript files ...
Checking for icecc compiler...(cached) no
Checking for C library cppunit... no
cppunit library missing

However, libcppunit is installed on the system:
ls /usr/lib64/libcppunit*
/usr/lib64/libcppunit-1.12.so.0 /usr/lib64/libcppunit.a /usr/lib64/libcppunit.so
/usr/lib64/libcppunit-1.12.so.0.0.0 /usr/lib64/libcppunit.la

When the CheckLlib is commented in the SConstruct, the compilation works flawlessly and the unit tests run without errors.

for lib in ['cppunit', 'python2.5']:
- if conf.CheckLib(lib):
+# if conf.CheckLib(lib):
         externalLIBS.append(lib)
- else:
- print lib+ ' library missing'
- Exit(1)
+# else:
+# print lib+ ' library missing'
+# Exit(1)

This happens on a openSUSE 11.0 (X86-64) system as well as on a Fedora release 8 (Werewolf) (X86-64) system.