Bump buildroot to 2019.02

bsp/buildroot/board/qemu/riscv32-virt/linux.config

@@ -0,0 +1,23 @@
+CONFIG_ARCH_RV32I=y
+CONFIG_SMP=y
+CONFIG_NR_CPUS=8
+CONFIG_PCI=y
+CONFIG_SYSVIPC=y
+CONFIG_NET=y
+CONFIG_PACKET=y
+CONFIG_UNIX=y
+CONFIG_INET=y
+# CONFIG_WIRELESS is not set
+CONFIG_VIRTIO_BLK=y
+CONFIG_NETDEVICES=y
+CONFIG_VIRTIO_NET=y
+# CONFIG_ETHERNET is not set
+# CONFIG_WLAN is not set
+CONFIG_SERIAL_8250=y
+CONFIG_SERIAL_8250_CONSOLE=y
+CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_VIRT_DRIVERS=y
+CONFIG_VIRTIO_MMIO=y
+CONFIG_EXT2_FS=y
+CONFIG_EXT4_FS=y
+CONFIG_TMPFS=y

bsp/buildroot/board/qemu/riscv32-virt/readme.txt

@@ -0,0 +1,7 @@
+Run the emulation with:
+
+  qemu-system-riscv32 -M virt -kernel output/images/bbl -append "root=/dev/vda ro console=ttyS0" -drive file=output/images/rootfs.ext2,format=raw,id=hd0 -device virtio-blk-device,drive=hd0 -netdev user,id=net0 -device virtio-net-device,netdev=net0 -nographic
+
+The login prompt will appear in the terminal that started Qemu.
+
+Tested with QEMU 2.12.1