
Fixes a regression introduced by Homebrew/homebrew#47950 in 9e3ee3e causing build failures with the error cabal: The file does not exist ''. This will occur whenever the optional :flags key isn't in the options hash passed to install_cabal_package. Closes Homebrew/homebrew#49425. Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>