[richard-burhans]

Fixes #46.

check_shell used $(echo $0), which make expands as a variable reference — a variable named echo $0, undefined, so empty — before the recipe reaches the shell. The test became [ != "-bash" ], a syntax error with no left operand, so [ exited non-zero and the else branch ran. The target printed "successfully passed" unconditionally on any shell, and only ever echod, so check could not gate on it either.

Escaping to $$(echo $$0) is not sufficient: $0 in a recipe is the shell make spawned (/bin/sh), never the string -bash, which is argv[0] of an interactive login shell. That variant fails unconditionally instead.

This tests $BASH_VERSION and sets SHELL := /bin/bash so recipes actually run under bash rather than dash on Debian/Ubuntu — which is what the check was asserting all along. The two changes go together: without the SHELL line, a BASH_VERSION test would fail on any system where /bin/sh is dash.

$ make check_shell            # bash
bash detected (5.3.9(1)-release); shell type check successfully passed   # exit 0

$ make SHELL=/bin/dash check_shell
ERROR: TOGA2 currently only supports bash as operating shell. ...
make: *** [Makefile:60: check_shell] Error 1                             # exit 1

Recipes were scanned for sh-isms (echo -e, source, [[, local, shell functions) — there are none — and every phony target dry-runs clean, so running them under bash changes nothing else.