ghci wrapper generated by Hadrian doesn't work via symlink

Summary

ghci wrapper script generated by Hadrian doesn't work if it is called via a symbolic link in a different directory.

Steps to reproduce

On a Mac with ghcup,

$ ghcup install ghc 9.2.1
$ ghcup unset ghc
$ ~/.ghcup/bin/ghci-9.2.1

Then I get

/Users/aratamizuki/.ghcup/bin/ghci-9.2.1: line 12: /Users/aratamizuki/.ghcup/bin/ghc: No such file or directory
/Users/aratamizuki/.ghcup/bin/ghci-9.2.1: line 12: exec: /Users/aratamizuki/.ghcup/bin/ghc: cannot execute: No such file or directory

The situation is,

• ~/.ghcup/bin/ghci-9.2.1 is a symlink to ~/.ghcup/ghc/9.2.1/bin/ghci
• ~/.ghcup/ghc/9.2.1/bin/ghci is a symlink to ~/.ghcup/ghc/9.2.1/bin/ghci-9.2.1
• ~/.ghcup/ghc/9.2.1/bin/ghci-9.2.1 contains:

#!/bin/sh
exedir="/Users/aratamizuki/.ghcup/ghc/9.2.1/lib/ghc-9.2.1/bin"
exeprog="ghci-9.2.1"
executablename="/Users/aratamizuki/.ghcup/ghc/9.2.1/lib/ghc-9.2.1/bin/ghci-9.2.1"
bindir="/Users/aratamizuki/.ghcup/ghc/9.2.1/bin"
libdir="/Users/aratamizuki/.ghcup/ghc/9.2.1/lib/ghc-9.2.1/lib"
docdir="/Users/aratamizuki/.ghcup/ghc/9.2.1/share/doc/ghc-9.2.1"
includedir="/Users/aratamizuki/.ghcup/ghc/9.2.1/include"

DIR=`dirname "$0"`
executable="$DIR/ghc"
exec $executable --interactive "$@"

Here, $DIR becomes the directory of the symlink (~/.ghcup/bin), not the wrapper script (~/.ghcup/ghc/9.2.1/bin). It should probably use $bindir instead of `dirname $0`.

Expected behavior

GHCi should start.

Environment

• GHC version used: GHC 9.2.1
• Operating System: macOS 11
• System Architecture: x86_64 or arm64