gcc@4.9.rb: Use CHILD_STATUS for Linuxbrew
gcc@4.9.rb: Use CHILD_STATUS for Linuxbrew

We have not bottle here, this just helps for merges,
as brew audit will fail with the old syntax

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