genie binary causes failing build on Ubuntu 18.04

[dprandle]

The linux build makefiles (linux-release64 and linux-debug64) fail saying genie requires glibc 2.29 - ubuntu 18.04 uses 2.27

../bx/tools/bin/linux/genie: /lib/x86_64-linux-gnu/libm.so.6: version 'GLIBC_2.29' not found (required by ../bx/tools/bin/linux/genie)

This could go under bx issue but since it causes build to fail for bgfx linux I though it made sense here.

The simple work-around for any Ubuntu 18.04 users out there - just build genie yourself and replace the binary in bx with your build. Luckily, genie is very easy to build.

Not sure if this is an issue where genie should simply be updated and my build of genie works because its newer, or if it is because genie is a binary built on a machine that uses glibc 2.29. If its the second option, perhaps adding the source code and building genie as part of bgfx build would work?