dri: Ensure subdirs have finished before linking driver
dri: Ensure subdirs have finished before linking driver

Recursive make is hard. If there are subdirectories in the DRI drivers,
it's pretty certain we want to finish building in them before linking
the driver. Add a new target to serialize the rules.

Signed-off-by: Dan Nicholson <2570c412b7cbb4203ff39baaca2bd49e72848226@gmail.com>

jbarczak/glsl-optimizer,mcanthony/glsl-optimizer,djreep81/glsl-optimizer,wolf96/glsl-optimizer,KTXSoftware/glsl2agal,tokyovigilante/glsl-optimizer,zeux/glsl-optimizer,zeux/glsl-optimizer,bkaradzic/glsl-optimizer,adobe/glsl2agal,jbarczak/glsl-optimizer,dellis1972/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,mcanthony/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,wolf96/glsl-optimizer,benaadams/glsl-optimizer,metora/MesaGLSLCompiler,zeux/glsl-optimizer,metora/MesaGLSLCompiler,bkaradzic/glsl-optimizer,dellis1972/glsl-optimizer,benaadams/glsl-optimizer,zz85/glsl-optimizer,mapbox/glsl-optimizer,KTXSoftware/glsl2agal,mcanthony/glsl-optimizer,wolf96/glsl-optimizer,mapbox/glsl-optimizer,bkaradzic/glsl-optimizer,bkaradzic/glsl-optimizer,adobe/glsl2agal,dellis1972/glsl-optimizer,adobe/glsl2agal,metora/MesaGLSLCompiler,bkaradzic/glsl-optimizer,djreep81/glsl-optimizer,mapbox/glsl-optimizer,mapbox/glsl-optimizer,zeux/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,wolf96/glsl-optimizer,mcanthony/glsl-optimizer,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,wolf96/glsl-optimizer,adobe/glsl2agal,zz85/glsl-optimizer,benaadams/glsl-optimizer,adobe/glsl2agal,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,zz85/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,KTXSoftware/glsl2agal,mapbox/glsl-optimizer,tokyovigilante/glsl-optimizer,tokyovigilante/glsl-optimizer,tokyovigilante/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,tokyovigilante/glsl-optimizer,zeux/glsl-optimizer,KTXSoftware/glsl2agal,KTXSoftware/glsl2agal