Merge branch 'wip/add-hgmp' into 'master'

ci: Add hgmp to the default build

See merge request ghc/head.hackage!102

ci/build-deps.nix

@@ -10,4 +10,5 @@ with pkgs;
   bzlib = [ bzip2 ];
   hmatrix = [ blas liblapack ];
   hexpat = [ expat ];
+  hgmp = [ gmp ];
 }

ci/config.sh

@@ -99,6 +99,7 @@ extra_package generic-lens
 extra_package microstache
 extra_package singletons
 extra_package servant
+extra_package hgmp
 
 # Build-tool packages
 build_tool_package alex