System frameworks cannot be loaded on macOS Big Sur

Summary

When running on macOS Big Sur, attempting to load a system framework at runtime fails with a not found error.

Steps to reproduce

Create a file called Main.hs with the following content:

module Main where

main = putStrLn "Hi."

Run it with runghc, passing -framework OpenGL to GHC:

runghc --ghc-arg="-framework OpenGL" Main.hs

Expected behavior

The program should run and say hi.

Environment

• GHC version used: 8.10.1
• Operating System: macOS 10.16 Big Sur (20A4300b)
• System Architecture: x86_64

Proposed Fix

Merge request !3689 (closed) is a proposed fix.

Remarks

This is presumably due to the following change in macOS Big Sur:

New in macOS Big Sur 11 beta, the system ships with a built-in dynamic linker cache of all system-provided libraries. As part of this change, copies of dynamic libraries are no longer present on the filesystem. Code that attempts to check for dynamic library presence by looking for a file at a path or enumerating a directory will fail. Instead, check for library presence by attempting to dlopen() the path, which will correctly check for the library in the cache. (62986286)

(https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11-beta-release-notes/)

The fix proposed above implements the behavior suggested there.