gcc: Disable multilib for Linuxbrew
gcc: Disable multilib for Linuxbrew

Fix error: gnu/stubs-32.h: No such file or directory

Fixes https://github.com/Linuxbrew/brew/issues/488

Closes Linuxbrew/homebrew-core#4246.

Signed-off-by: Michka Popoff <7b0496f66f66ee22a38826c310c38b415671b832@gmail.com>

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