minigbm: virtio_gpu: select dumb/virgl at runtime.

For using same image on legacy-qemu and virgl enabled qemu. We need
to handle dumb and virgl code path at run time. Just merge them to
one driver.

BUG=b:77302150
TEST=manual - run novato image under qemu with gl=on/off.

Change-Id: Ia12140fba16a350fe13f4258d25333ecfe8352b3
Reviewed-on: https://chromium-review.googlesource.com/998631
Commit-Ready: Lepton Wu <lepton@chromium.org>
Tested-by: Lepton Wu <lepton@chromium.org>
Reviewed-by: Lepton Wu <lepton@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
diff --git a/Android.mk b/Android.mk
index 0abeaf4..e75766f 100644
--- a/Android.mk
+++ b/Android.mk
@@ -26,8 +26,7 @@
 	udl.c \
 	vc4.c \
 	vgem.c \
-	virtio_dumb.c \
-	virtio_virgl.c
+	virtio_gpu.c
 
 MINIGBM_CPPFLAGS := -std=c++14 -D_GNU_SOURCE=1 -D_FILE_OFFSET_BITS=64
 MINIGBM_CFLAGS := -Wall -Wsign-compare -Wpointer-arith \
@@ -40,11 +39,6 @@
 LOCAL_SHARED_LIBRARIES += libdrm_intel
 endif
 
-ifneq ($(filter virgl, $(BOARD_GPU_DRIVERS)),)
-MINIGBM_CPPFLAGS += -DDRV_VIRGL
-MINIGBM_CFLAGS += -DDRV_VIRGL
-endif
-
 ifneq ($(filter meson, $(BOARD_GPU_DRIVERS)),)
 MINIGBM_CPPFLAGS += -DDRV_MESON
 MINIGBM_CFLAGS += -DDRV_MESON