xcb: don't build-depend on python-native

xcb-proto had a dependency on python-native as it builds and installs a Python
module, but xcb-proto is very low in the build to force a dependency on
python-native.

As it turns out libxcb simply asks pkg-config for the full path to the module
xcb-proto installed and uses it directly so there is no need to build
python-native.  Instead replace AM_PATH_PYTHON with two explicit variable
definitions (need to set PYTHON for automake's install logic).

Also remove the dependency on xcb-proto-native as libxcb uses the data files and
tooling from the target sysroot, and patching it to use the native sysroot adds
complication for no good reason.

(From OE-Core rev: bc38ef47b05128623a916172c2cfd244510b201e)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-graphics/xorg-proto/xcb-proto/no-python-native.patch

@@ -0,0 +1,27 @@
+Upstream uses AM_PATH_PYTHON to find a python binary and ask it where to install
+libraries.  This means we either need to depend on python-native (large build
+dependency, early in the build) or use the host python (pythondir reflects the
+host and not the target, breaks builds).
+
+The third option is to just hardcode the path where the module goes, as most
+callers of the code use pkg-config to find where it was installed anyway.
+
+Upstream-Status: Inappropriate
+Signed-off-by: Ross Burton <ross.burton@intel.com>
+
+diff --git a/configure.ac b/configure.ac
+index d140bfe..c7b68da 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -14,7 +14,10 @@ if test "$XMLLINT" = "no"; then
+    AC_MSG_WARN([xmllint not found; unable to validate against schema.])
+ fi
+
+-AM_PATH_PYTHON([2.5])
++pythondir="${libdir}/xcb-proto"
++AC_SUBST(pythondir)
++PYTHON="python"
++AC_SUBST(PYTHON)
+
+ xcbincludedir='${datadir}/xcb'
+ AC_SUBST(xcbincludedir)