configs: Enable the EROFS read-only filesystem #3480

Job	Run time
build (bcm2835, arm, bcm2835_defconfig, kernel)	10m 17s
build (arm64, arm64, defconfig, kernel8)	39m 24s
build (bcmrpi, arm, bcmrpi_defconfig, kernel)	31m 5s
build (bcm2709, arm, bcm2709_defconfig, kernel7)	32m 19s
build (bcm2711, arm, bcm2711_defconfig, kernel7l)	34m 4s
build (bcm2711_arm64, arm64, bcm2711_defconfig, kernel8)	43m 36s
build (bcm2711_rt, arm64, bcm2711_rt_defconfig, kernel8_rt)	42m 35s
build (bcm2712, arm64, bcm2712_defconfig, kernel_2712)	42m 20s
	4h 35m 40s

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