Add configure.fish, a wrapper of configure.sh for fish shell.

[jonasschwab]

Adds a Fish shell wrapper around configure.sh so Fish users can set up the ALF build environment by sourcing a Fish script, while still reusing the existing POSIX configure.sh logic.

Changes

• Introduces configure.fish to invoke configure.sh in a POSIX sh subshell, using portable mktemp fallback for BSD/macOS compatibility.
• Passes paths as positional parameters to sh -c to correctly handle spaces and special characters.
• Captures the resulting environment and imports ALF_* variables into the current Fish session.
• Guards against incorrect usage: errors with a clear message if the script is not sourced inside an interactive Fish shell session (e.g. executed directly or sourced from bash/sh).

Usage

source configure.fish MACHINE [MODE] [STAB] [options]
# or
. configure.fish MACHINE [MODE] [STAB] [options]

See configure.sh for the full list of MACHINE, MODE, STAB, and option values.

[Copilot]

Pull request overview

Adds a Fish-shell wrapper around configure.sh so Fish users can set up the ALF build environment by sourcing a Fish script, while still reusing the existing POSIX configure.sh logic.

Changes:

• Introduces configure.fish to invoke (source) configure.sh in a POSIX sh subshell.
• Captures the resulting environment and imports ALF_* variables into the current Fish session.

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[jonasschwab]

@copilot Please add a check to configure.fish that checks if it is indeed sourced by a fish shell.

[Copilot]

@copilot Please add a check to configure.fish that checks if it is indeed sourced by a fish shell.

Added two guards at the top of configure.fish (commit configure.fish: add check that the script is sourced in fish):

1. Fish shell check – set -q FISH_VERSION is true only when running inside fish; any attempt to source the script from bash/sh prints an error and exits.
2. Sourced check – status --is-interactive is true in an interactive fish session. When the script is executed directly (fish configure.fish), fish runs it as a non-interactive subprocess and this check prints an error with the correct source usage.