meson+autotools: get rid of spammy GCC warning -Wformat-truncation

meson+autotools: get rid of spammy GCC warning -Wformat-truncation

That warning fires every time a string function takes an argument that
could possibly be longer than its max output, which triggers all over
the place, especially when working with file paths ("what if every file
path is MAX_PATH long?" is what GCC is saying, which is really annoying
when we *know* that "/dev/dri/cardN" is not gonna be 4096 char long and
it's safe to store it in a 32-char array).

Anyway, we either add a ton of dead code all over the place to make GCC
happy, or we get rid of its spam. I chose the latter.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>