targets/dri-i915: Force c++ linker in all cases
targets/dri-i915: Force c++ linker in all cases

NOTE: This is a candidate for the 9.1 branch.
Bugzilla: https://bugs.gentoo.org/show_bug.cgi?id=461696
Reviewed-by: Andreas Boll <041cac00e0cb793452cecf5c52a77db13d069cf3@gmail.com>

metora/MesaGLSLCompiler,dellis1972/glsl-optimizer,djreep81/glsl-optimizer,zeux/glsl-optimizer,bkaradzic/glsl-optimizer,benaadams/glsl-optimizer,zeux/glsl-optimizer,mapbox/glsl-optimizer,tokyovigilante/glsl-optimizer,mapbox/glsl-optimizer,djreep81/glsl-optimizer,bkaradzic/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,mcanthony/glsl-optimizer,benaadams/glsl-optimizer,tokyovigilante/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,benaadams/glsl-optimizer,wolf96/glsl-optimizer,dellis1972/glsl-optimizer,mapbox/glsl-optimizer,bkaradzic/glsl-optimizer,jbarczak/glsl-optimizer,tokyovigilante/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,zz85/glsl-optimizer,zeux/glsl-optimizer,wolf96/glsl-optimizer,wolf96/glsl-optimizer,mcanthony/glsl-optimizer,jbarczak/glsl-optimizer,tokyovigilante/glsl-optimizer,mcanthony/glsl-optimizer,bkaradzic/glsl-optimizer,mcanthony/glsl-optimizer,zeux/glsl-optimizer,djreep81/glsl-optimizer,djreep81/glsl-optimizer,zz85/glsl-optimizer,mapbox/glsl-optimizer,dellis1972/glsl-optimizer,benaadams/glsl-optimizer,wolf96/glsl-optimizer,mapbox/glsl-optimizer,bkaradzic/glsl-optimizer,wolf96/glsl-optimizer,mcanthony/glsl-optimizer,tokyovigilante/glsl-optimizer,benaadams/glsl-optimizer,zeux/glsl-optimizer