sysroot and json.h

[Jeffrey Bastian]

In January, commit 690de7ffb96c changed the Makefile.am files to use gcc
sysroot support for the json headers and libraries:
    http://kernel.ubuntu.com/git?p=hwe/fwts.git;a=commit;h=690de7ffb96c

This is breaking the build process on Fedora 21:
=======================================================================
libtool: compile:  gcc -DHAVE_CONFIG_H .... -I=/usr/include/json -I=/usr/include/json-c .... -c fwts_ac_adapter.c -fPIC -DPIC -o .libs/libfwts_la-fwts_ac_adapter.o
In file included from ../../../src/lib/include/fwts.h:84:0,
                 from fwts_ac_adapter.c:19:
../../../src/lib/include/fwts_json.h:23:18: fatal error: json.h: No such file or directory
 #include <json.h>
                  ^
compilation terminated.
=======================================================================

The json.h file is in /usr/include/json-c/json.h where it's supposed to
be, it's just that the -I= flag isn't working without --sysroot too.

I can manually compile this file if I re-run the above command and add a
"--sysroot=/" flag, so I tried doing
    ./configure --with-sysroot=/
    make
but the "--with-sysroot" flag to configure does not add a "--sysroot"
flag to the gcc command line so that didn't work.

Then I tried
    CFLAGS=--sysroot=/ ./configure
but that failed in the configure script.

So for now I have to revert this patch to get it to compile.

Can the -I= for json.h only be used if you also have --sysroot defined?
That is, it should be either
    --sysroot=/some/path -I=/usr/include/json -I=/usr/include/json-c
(exclusive-)or
    -I/usr/include/json -I/usr/include/json-c

Thank you,
Jeff Bastian