ponyc: add HEAD.
ponyc: add HEAD.

Bug in 0.1.7 causing segfaults during compliation fixed in master.

Closes #43597.

Signed-off-by: Mike McQuaid <a17fed27eaa842282862ff7c1b9c8395a26ac320@mikemcquaid.com>

kwilczynski/homebrew,kwilczynski/homebrew,kwilczynski/homebrew,kwilczynski/homebrew