[Bug target/77326] [avr] Invalid optimization using varargs and a weak function

[matthijs at stdin dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77326

--- Comment #1 from Matthijs Kooijman <matthijs at stdin dot nl> ---
The original reporter just added a comment that this does not occur anymore in
gcc 6.1.0, though I haven't got anything newer than 5.1 available here to
check.