Using the latest (as of today) gcc-arm-embedded toolchain caused two build
failures similar to:
error: unknown type name 'cookie_io_functions_t'
These custom IO functions are now protected by a define, so define _GNU_SOURCE
which enables all such areas. This is a libc issue.
Signed-off-by: Trevor Woerner <twoerner@gmail.com>
While nano specs are certainly handy, it should be documented how to use them,
not turned on by default. People with otherwise valid toolchains, who might
simply not care about nano specs are unable to build the examples with these
options.
