Support building script on Arch Linux

[FallingSnow]

Arch Linux sets python to python 3 and python2 to python 2.

Script's CMakeLists.txt hard codes the python command.

servo/components/script/CMakeLists.txt

Line 64 in 53d9ca1

COMMAND python -B ${bindings_src}/pythonpath.py -I ${bindings_src}/parser -I ${bindings_src}/ply

In order to select the correct python version

find_package( PythonInterp 2 REQUIRED )

should be added to the top of the file and all python commands should be replaced with

${PYTHON_EXECUTABLE}

so the above reads

COMMAND ${PYTHON_EXECUTABLE} -B ${bindings_src}/pythonpath.py -I ${bindings_src}/parser -I ${bindings_src}/ply 

P.S. This is supported by the minimum cmake version 2.6

[kwonoj]

It'd be good to support build script on arch ooto. Mind if I shoot small PR for it? @FallingSnow (only if you don't have plan to tackle this)

[FallingSnow]

By all means, please. I have too many other obligations to submit a PR otherwise I would have already :)

[kwonoj]

@FallingSnow thanks, let me try to stab on this.

[kwonoj]

@highfive : assign me

[highfive]

Hey @kwonoj! Thanks for your interest in working on this issue. It's now assigned to you!