configure already preferred the system readline (AC_CHECK_LIB → -lreadline) and
only fell back to the bundled readline/ copy. Remove that fallback: a non-Tcl
interactive build now requires the *system* GNU readline -- both its header
(AC_CHECK_HEADER readline/readline.h, so configure fails cleanly instead of deep
in compilation) and the library -- and if neither Tcl nor readline is available
configure errors with a clear explanation of the three ways forward (build with
Tcl, install libreadline-dev, or --disable-readline).
Also drop the now-meaningless --enable-readline-bundled, and substitute
MAKE_READLINE=0 unconditionally so the Makefiles' bundled-readline path goes
inert. readline/ and all Makefiles are left untouched here (cleaned up and
removed in the following patches).
--disable-readline stays as the escape hatch: it just tells configure to ignore
the system readline and build the existing no-line-editing variant.
Verified: Tcl build rc=0 (readline off, 375 files, readline/ not built); non-Tcl
--disable-readline builds (serial); non-Tcl default with no readline dev package
now errors with the guidance message.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
c05ac60851