gcc/Makefile.in: Always check info dependencies

gcc/Makefile.in: Always check info dependencies

BUILD_INFO is currently a byproduct of checking makeinfo
presence/version.  INSTALL_INFO used to be defined similarly, but was
removed in 2000 (!) by commit 17db658241d18cf6db59d31bc2d6eac96e9257df
(svn r38141).

In order to save build time, our CI overrides MAKEINFO=echo, which
works when invoking 'make all' but not for 'make install' in case some
info files need an update.

I noticed this while testing a patch posted on the gcc-patches list,
leading to an error at 'make install' time after updating tm.texi (the
build reported 'new text' in tm.texi and stopped).  This is because
'install' depends on 'install-info', which depends on
$(DESTDIR)$(infodir)/gccint.info (among others).

As discussed, it is better to detect this problem during 'make all'
rather than 'make install', and we still want to detect it even if
makeinfo is not available.

This patch makes configure set BUILD_INFO=no-info in case makeinfo is
missing/too old, which effectively makes the build rules no-ops
(x$(BUILD_INFO) != xinfo), and updates Makefile.in so that 'info'
dependencies are still checked.

2024-02-10  Christophe Lyon  <christophe.lyon@linaro.org>

	gcc/
	* Makefile.in: Add no-info dependency.
	* configure.ac: Set BUILD_INFO=no-info if makeinfo is not
	available.
	* configure: Regenerate.