cwirc version 2.0.0-4 failed to build on amd64 with GCC-4.6/oneiric

cwirc version 2.0.0-4 failed to build on amd64 with GCC-4.6/oneiric
Link to failed build: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2448039

Details about the rebuild:
https://lists.ubuntu.com/archives/ubuntu-devel/2011-April/033042.html

Direct link to the build log: https://launchpad.net/ubuntu/+archive/test-rebuild-20110413/+buildjob/2448039/+files/buildlog_ubuntu-natty-amd64.cwirc_2.0.0-4_FAILEDTOBUILD.txt.gz

This log snippet might be of interest, since it triggered the matcher 'Purging chroot-autobuild'.
Excerpt 2469 lines into the build log:

grid.c:(.text+0x2ca): undefined reference to `cos'
grid.c:(.text+0x2df): undefined reference to `cos'
grid.c:(.text+0x300): undefined reference to `sin'
grid.c:(.text+0x346): undefined reference to `atan2'
grid.c:(.text+0x362): undefined reference to `sqrt'
grid.c:(.text+0x37c): undefined reference to `sqrt'
cwsound.o: In function `generate_cw_sound_fragment':
cwsound.c:(.text+0x73): undefined reference to `sin'
collect2: ld returned 1 exit status
make[2]: *** [cwirc_frontend] Error 1
make[2]: Leaving directory `/build/buildd/cwirc-2.0.0'
make[1]: *** [override_dh_auto_build] Error 2
make[1]: Leaving directory `/build/buildd/cwirc-2.0.0'
make: *** [build] Error 2
dpkg-buildpackage: error: debian/rules build gave error exit status 2
******************************************************************************
Build finished at 20110421-2347
FAILED [dpkg-buildpackage died]
Purging chroot-autobuild/build/buildd/cwirc-2.0.0