[bug] wierd triangle holes on linux

Today I setup a basic project just by using the TPS template and I setup some things…
I disable all except following platform: IOS, Android and HTML5
I’ve set the project’s quality to “scalable 2D/3D” and “mobile/tablet target”
and I just drag and drop some default material…
Then I push “Build” button and BOOM this is what happen:

Like you see on the picture not all poly are “triangled”…

I am on the “release” branch my pull was made on 2 april at 22:30 (Korean hour) so my unreal version is 4.7.3

my hardware is: 2.1GHz AMD A8-5550M APU with Radeon (8550G)

My system is: Gentoo kernel 3.18.9 with Xorg 1.15.2 and proprietary drivers fglrx (with the “Software Driver packaging version” 14.501.1003)