The opencascade patch intrusively checked against libraries but broke
some build scripts. This restores the default cmake OCE behavior that was
changed by 2bab30d9a and makes the OpenCascade search truly secondary.
This changes the IGES import parameter precision to be file-defined
instead of hard-coded in KiCad. OCE-0.18 does not handle faces with
a set of points whose approximation creates a single point.
By allowing the file to set the precision level, we leave it to the
generating program to create a file with non-degenerate faces.
Fixes: lp:1738872
* https://bugs.launchpad.net/kicad/+bug/1738872