Difficulty building older Emacsen: <tab> characters seemingly fouling things up.

[Alan Mackenzie]

Hello, Emacs.

Recently, I've had to rebuild some older Emacsen because libraries they
depend on have been updated.  An example is Emacs 23.1.  I'm running on
an up to date GNU system (Gentoo, to be precise).

I reconfigured this (with ./configure --with-gpm --without-tiff
--without-gif), then attempted to build it (with make -j5, or make -j5
bootstrap).

This instantly bails out with a make error in .../lib-src:

    make[1]: Entering directory '/usr/local/src/emacs-23.1/lib-src'
    Makefile:144: *** recipe commences before first target.  Stop.
    make[1]: Leaving directory '/usr/local/src/emacs-23.1/lib-src'


Looking around L144 of .../lib-src/Makefile, I see this:

    # ========================== start of cpp stuff =======================
    LIBS_MOVE=$(KRB4LIB) $(DESLIB) $(KRB5LIB) $(CRYPTOLIB) $(COM_ERRLIB)
    $(HESIODLIB)
    LOADLIBES=
    ALL_CFLAGS = -D_BSD_SOURCE -DHAVE_CONFIG_H
    <tab..>  -I. -I../src -I${srcdir} -I${srcdir}/../src ${LDFLAGS}   <--- 144
    ${CPPFLAGS} ${CFLAGS}

.  There is a <tab> at the beginning of L144 fouling up the Makefile.

Somehow it seems that recent versions of the configuration toolchain
(whatever that means) are incompatible with older configure scripts.
23.1 was before we had autogen.h in the top directory.

Would somebody familiar with the configuration process please help me
understand what's happening here, so that I can fix it.  Thanks!

-- 
Alan Mackenzie (Nuremberg, Germany).