make: Entering directory '/home/rclinux/rc-buildroot-test/scripts/instance-1/buildroot'
/usr/bin/make -j1 O=/home/rclinux/rc-buildroot-test/scripts/instance-1/output HOSTCC="/usr/bin/gcc" HOSTCXX="/usr/bin/g++" silentoldconfig
make[1]: Entering directory '/home/rclinux/rc-buildroot-test/scripts/instance-1/buildroot'
  GEN     /home/rclinux/rc-buildroot-test/scripts/instance-1/output/Makefile
make[1]: Leaving directory '/home/rclinux/rc-buildroot-test/scripts/instance-1/buildroot'

Your Buildroot configuration needs a compiler capable of building 32 bits binaries.
If you're running a Debian/Ubuntu distribution, install the g++-multilib package.
For other distributions, refer to their documentation.
support/dependencies/dependencies.mk:22: recipe for target 'core-dependencies' failed
make: *** [core-dependencies] Error 1
make: Leaving directory '/home/rclinux/rc-buildroot-test/scripts/instance-1/buildroot'