simavr: fix tarball URL

[fauxpark]

URL was incorrect. Also bumped to generate new bottles.

[fauxpark]

Looks like this is broken. The makefile logic checks that a folder exists in the cellar named avr-gcc*, which works in bash but not zsh:

   ifneq (${shell test -d $(HOMEBREW_PREFIX)/Cellar/avr-gcc* && echo Exists}, Exists)
    $(error Please install avr-gcc: brew tap osx-cross/homebrew-avr ; brew install avr-libc)
   endif

(The error message is also wrong; avr-libc no longer exists as a separate formula).