In order to add FSharp.Core.dll to the Mono GAC the DLL needs to be
re-signed with the mono.snk key. The mono.snk key is available from
the 'Mono Sources'.
http://www.mono-project.com/
http://anonsvn.mono-project.com/source/trunk/mcs/class/mono.snk
To proceed with a Mono GAC install, obtain mono.snk, put it in the
current directory and re-run this script.
An alternative to installing the DLLs in the Mono GAC is to add the
FSharp bin directory to the MONO_PATH variable. For more information
on 'How Mono Finds Assemblies' see http://www.mono-project.com/Gacutil
Arch Linux