Give include priority to the SIP include path.

[kakaroto]

This causes an issue with cura-build if a newer SIP version is installed on the system,
then the python include path would take precedence and Arcus would require
a newer SIP API than the one that comes bundled with cura.

This will finally get rid of this error if sip 4.18 is installed locally while Arcus gets compiled by the cura-build script :

An uncaught exception has occurred!
Traceback (most recent call last):
  File "./bin/cura2", line 47, in <module>
    import Arcus #@UnusedImport
Runtime Error: the sip module implements API v11.0 to v11.2 but the Arcus module requires API v11.3

[nickthetait]

Any update on this one?

[Ghostkeeper]

I don't feel qualified enough to judge the impact of this change. I'd like @awhiemstra or @sedwards2009 to take a look at it.

[thopiekar]

For me this change makes sense. You can blame it on me if it breaks something 🙈