host-libxml2: Prefer python2 when python3 is also installed

Fixes mesa3d build errors:
http://autobuild.buildroot.net/results/d10/d105a0b3ca11fad34f9a2dae0dae9bd041d918a6/
http://autobuild.buildroot.net/results/d71/d7121443715024d15a66ff1abf1261803c10cd35/
http://autobuild.buildroot.net/results/ce6/ce64164d76972f82acab277afc9c95a876c6433e/

checking for python2... python2
checking python2 module: libxml2... no
configure: error: failed to find required module libxml2
make: *** [/home/test/test/1/output/build/mesa3d-10.0.4/.stamp_configured] Error 1

mesa3d needs python2 bindings installed by libxml2. To enforce their build
option BR2_PACKAGE_HOST_LIBXML2_PYTHON is used exclusively by mesa3d so this
patch does not affect other packages.

Without this patch host-libxml2 installs the python bindings in
$(HOST_DIR)/usr/lib/$(PYTHON3_VERSION_MAJOR) using this defconfig:

BR2_PACKAGE_MESA3D=y
BR2_PACKAGE_PYTHON3=y

because $(HOST_DIR)/usr/bin/python points to $(HOST_DIR)/usr/bin/python3:

Quote from host-libxml2 configure log:
Found python in /home/fli4l/br2/buildroot/output/host/usr/bin/python
Found Python version 3.4

HOST_$(PACKAGE)_NEEDS_HOST_PYTHON does not work here because libxml2 does
not use the python-package infrastructure.

libxml2-python2.patch extends the python detection code in host-libxml2 to
first look for python2, to keep the patch small I did not update the indentions:

Found python2 in /home/fli4l/br2/buildroot/output/host/usr/bin/python2
Found Python version 2.7

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Tested-by: Samuel Martin <s.martin49@gmail.com>
host-nodejs: use the standard configure options

Also cleanup leading whitespace.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
host-nodejs: enforce using python2 interpreter during the build

nodejs build system is based on python, and it does not support python3.

This patch makes sure python2 is used for the build.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
host-omniorb: force python interperter

Omniorb build-system requires python2 interpreter.

By default, it looks for python program, which may fallback on the system
python interpreter in case python is disabled and python3 is enabled.

So, this patch enforces the python interpreter to python2 built by
Buildroot.

Fixes:
  http://autobuild.buildroot.org/results/b4f/b4f3a2602ba0224ac3253c4bf6ed87ec045df772/

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
host-python-pyrex: use the HOST_*_NEEDS_HOST_PYTHON infrastructure

This will automatically take care of adding the right host-python package
to the dependency list and it will avoid trying to build python-pyrex using
python3.

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
openpgm: make its build system python2/python3 friendly

This patch fixes build issue when python3 is enabled, and host python2
interpreter is not available.

Fixes:
  http://autobuild.buildroot.net/results/01f/01f886a073439c0639ed93e596b68bcadf1a5824/

Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Cc: Baruch Siach <baruch@tkos.co.il>

---

Note that, though current openpgm trunk (svn+1508) supports python2 and
python3, I have not backported the upstream patch because
version_generator.py has been touched by several non-atomic change sets.