make: Entering directory `/home/peko/autobuild/instance-0/buildroot'
/usr/bin/make -j1 O=/home/peko/autobuild/instance-0/output HOSTCC="/usr/bin/gcc" HOSTCXX="/usr/bin/g++" silentoldconfig
  GEN     /home/peko/autobuild/instance-0/output/Makefile

Your Buildroot configuration needs a compiler capable of building 32 bits binaries.
If you're running a Debian/Ubuntu distribution, install the gcc-multilib package.
For other distributions, refer to their documentation.
make[1]: *** [core-dependencies] Error 1
make: *** [_all] Error 2
make: Leaving directory `/home/peko/autobuild/instance-0/buildroot'