egl/dri2: Fix build of dri2 egl driver with SCons
egl/dri2: Fix build of dri2 egl driver with SCons

* egl/dri2 was missing a SConscript
* Problem caught by Adrián Arroyo Calle

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler