Ports: Add MPFR

Required to build the toolchain inside Serenity.

Ports/mpfr/package.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env -S bash ../.port_include.sh
+port=mpfr
+version=4.1.0
+useconfigure=true
+configopts="--target=${SERENITY_ARCH}-pc-serenity --with-sysroot=/"
+files="https://ftpmirror.gnu.org/gnu/mpfr/mpfr-${version}.tar.xz mpfr-${version}.tar.xz
+https://ftpmirror.gnu.org/gnu/mpfr/mpfr-${version}.tar.xz.sig mpfr-${version}.tar.xz.sig
+https://ftpmirror.gnu.org/gnu/gnu-keyring.gpg gnu-keyring.gpg"
+auth_type="sig"
+auth_opts="--keyring ./gnu-keyring.gpg mpfr-${version}.tar.xz.sig"
+depends="gmp"

Ports/mpfr/patches/config.sub.patch

@@ -0,0 +1,11 @@
+--- mpfr-4.1.0/config.sub	2020-07-10 12:59:02.000000000 +0100
++++ mpfr-4.1.0.serenity/config.sub	2021-07-28 18:05:59.462525103 +0100
+@@ -1390,7 +1390,7 @@
+ 	      | -powermax* | -dnix* | -nx6 | -nx7 | -sei* | -dragonfly* \
+ 	      | -skyos* | -haiku* | -rdos* | -toppers* | -drops* | -es* \
+ 	      | -onefs* | -tirtos* | -phoenix* | -fuchsia* | -redox* | -bme* \
+-	      | -midnightbsd*)
++	      | -midnightbsd* | -serenity*)
+ 	# Remember, each alternative MUST END IN *, to match a version number.
+ 		;;
+ 	-qnx*)