qemu_v8: add scripts_gdb to LINUX_COMMON_FLAGS

Commit c993ec995a9e ("qemu_v8.mk: add scripts_gdb kernel build target")
has added "$(MAKE) -C $(LINUX_PATH) $(LINUX_COMMON_FLAGS) scripts_gdb" to the
linux: recipe. Since linux: depends on linux-common which already runs
"$(MAKE) -C $(LINUX_PATH) $(LINUX_COMMON_FLAGS)", and since
$(LINUX_COMMON_FLAGS) contains "Image", the Image target is made twice.
It is more efficient to remove the added line and add scripts_gdb to
LINUX_COMMON_FLAGS instead.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
Acked-by: Peter Griffin <peter.griffin@linaro.org>
diff --git a/qemu_v8.mk b/qemu_v8.mk
index dcf2220..ec5a8ed 100644
--- a/qemu_v8.mk
+++ b/qemu_v8.mk
@@ -218,10 +218,9 @@
 
 linux-defconfig: $(LINUX_PATH)/.config
 
-LINUX_COMMON_FLAGS += ARCH=arm64 Image
+LINUX_COMMON_FLAGS += ARCH=arm64 Image scripts_gdb
 
 linux: linux-common
-	$(MAKE) -C $(LINUX_PATH) $(LINUX_COMMON_FLAGS) scripts_gdb
 	mkdir -p $(BINARIES_PATH)
 	ln -sf $(LINUX_PATH)/arch/arm64/boot/Image $(BINARIES_PATH)