rtags: fix for linuxbrew
rtags: fix for linuxbrew

Closes Linuxbrew/linuxbrew#1022.

Signed-off-by: Piotr Gaczkowski <46f0c4ed049e7aff30e03b3686f185a0838667df@gmail.com>

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