[PATCH -next 2/2] kbuild: fix for updated LZ4 tool with the new streaming format

[Andrew Morton]

On Tue, 16 Jul 2013 00:47:27 -0700 Andrew Morton <akpm at linux-foundation.org> wrote:

> On Mon, 15 Jul 2013 15:08:20 -0700 "H. Peter Anvin" <hpa at zytor.com> wrote:
> 
> > On 07/15/2013 03:03 PM, Andrew Morton wrote:
> > > 
> > > I don't know how to do this.  Any suggestions?
> > > 
> > > It has to be done at `make config' time.  We'd need to probe for the
> > > presence of lz4c and then....  what?
> > > 
> > > Is there any precedent for this?
> > > 
> > > I don't think we can just ignore the absence of lz4c - the user has
> > > selected a config which his system cannot build.  The problem lies
> > > within randconfig itself.
> > > 
> > 
> > We keep running over the need to be able to have kconfig run tests on
> > the build system (for toolchain support or for optional tools needed);
> > running them in the Makefiles (i.e. at Kbuild time) is simply too late.
> > 
> 
> Would it make sense to extend Kconfig's `depends'?
> 
> 	depends on $(shell-command)
> 
> I don't know how practical that would be to implement...

Or, easier and faster, run some front-end script which generates
once-off Kconfig symbols.

	if [ -x /bin/lz4c ]
	then
		echo CONFIG_HAVE_LZ4C
	fi

then munge the output of that script into the Kconfig run and do

	depends on HAVE_LZ4C