error: cannot find -lclip2tri One needs to build 3rdparty/{clip2tri,poly2tri,clipper} to make it compile.
Attach full build log.
Created attachment 471608 [details] build.log
Same for qtpositioning-5.9.9999 of course. The fix is simple, change QT5_TARGET_SUBDIRS to: QT5_TARGET_SUBDIRS=( src/3rdparty/clipper src/3rdparty/poly2tri src/3rdparty/clip2tri src/positioning src/plugins/position/positionpoll )
Thanks! https://gitweb.gentoo.org/proj/qt.git/commit/?id=a61801aa797e50fa672b9db18104fc228e4f9f2b