chapel: Fix for Linuxbrew
chapel: Fix for Linuxbrew

See https://gist.github.com/04fb73154746b7e279d5

Message:
> Warning: tried to install empty array to /home/bob/.linuxbrew/Cellar/chapel/1.12.0/bin

Closes Linuxbrew/linuxbrew#876.
Closes Linuxbrew/linuxbrew#877.

Signed-off-by: Shaun Jackman <b580dab3251a9622aba3803114310c23fdb42900@gmail.com>

maxim-belkin/homebrew-core,forevergenin/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,LinuxbrewTestBot/homebrew-core,forevergenin/homebrew-core,maxim-belkin/homebrew-core,rwhogg/homebrew-core,Linuxbrew/homebrew-core,Linuxbrew/homebrew-core