mpfr: Fix for non-MacOS systems
mpfr: Fix for non-MacOS systems

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