Buildroot toolchain RPM packages

Here lie the configs and specs for the following buildroot toolchains:

 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-mipsel32-o32-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-mipsel64-n32-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-mipsel64-n64-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-armv6el-eabi-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-armv8-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-armv8be-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-powerpc-uclibc/
 - https://copr.fedorainfracloud.org/coprs/davidgf/buildroot-x86-64-muslc/

Toolchains include compiler & gdb, with static and shared libs (and sysroot with
all the shared libs).