elf2flt: use new upstream site and bump version

elf2flt: use new upstream site and bump version

The uClinux developers now have a Github with elf2flt code, with an
upstream that is again active. Let's switch to this upstream, which
has built-in support for ARM noMMU, contributed by Waldemar.

Since we're now fetching from github, a hash file is added as well.

Finally, we disable -Werror to avoid build issues caused by warnings.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>