automake: rework the EGL build

Simplify things by merging the two makefiles. This way we can combine
the duplicated HAVE_PLATFORM_ checks, and build the library without
having a separate static library.

v2: use $() when referencing variables, use correct define (Matt)

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/configure.ac b/configure.ac
index c25dc5d..480018a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2296,8 +2296,7 @@
 dnl Substitute the config
 AC_CONFIG_FILES([Makefile
 		src/Makefile
-		src/egl/drivers/dri2/Makefile
-		src/egl/main/Makefile
+		src/egl/Makefile
 		src/egl/main/egl.pc
 		src/egl/wayland/wayland-drm/Makefile
 		src/egl/wayland/wayland-egl/Makefile