xfconf: use sysroot and target perl

xfconf: use sysroot and target perl

xfconf-4.10.0 does not use OE sysroot as is.
--with-sysroot=yes
will make configure run CC --print-sysroot
and use that.

When searching the PATH for perl, no target perl is found,
since PATH does not contain any reference.
Instead native perl is found, and if certain perl packages
are installed on the host machine, the xfconf perl support
is enabled which may cause the build to fail on 64 bit hosts.
If the perl packages are not installed on the host, then
perl support in xfconf is disabled, and the xfconf build
will succeed, even on 64 bit hosts.

If native perl is found, and the perl packages are available
on the host, the perl support is enabled.

Since native perl is used, the native linker is used to link the
resulting *target* code.

The perl support requires some libraries, which are built for the target.
If the host is 64 bit (x86_64) and the target is 32 bit (ARM?),
there is a mismatch which is detected by the linker,
and the libraries found are rejected.

If the host does not have the correct libraries,
then the xfconf build fails.
If the host has the correct libraries, then the linker will try
to link host libraries with the target application.

The patch will define PERL as the target perl.
This means that configure will look for the required perl
packages in the target sysroot, instead of in the native filesystem.

The patch has been tested in Angstrom master, which does not
build the required perl packages, and thus perl support
in xfconf is disabled, and the build succeeds.

A simpler way to do this, proposed by Charles Ash <ashcharles@gmail.com>
is to simply disable the perl-support in xfconf.
This patch will be better, if ever the support for the needed
perl packages is added to the OpenEmbedded/Angstrom build.

(From meta-openembedded rev: 480d3338a7401f53e7b8a031294d37498a6a7be6)

Signed-off-by: Ulf Samuelsson <ulf@emagii.com>
Tested-by: Ash Charles <ashcharles@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>