Merge branch 'ivan/board_var' into 'master'

aarch64: support building Redox for different motherboard.

See merge request redox-os/redox!1388

HARDWARE.md

@@ -305,6 +305,22 @@ If you have a customized computer, put it here.
 
 Computers using a 64 bits ARM CPU.
 
+### Raspberry Pi
+
+- **Raspberry Pi 3 Model B+**
+
+```
+Status - Booting
+Redox version - 0.8.0
+Variant - server
+Image date - None
+
+- Booted using Uboot
+- Boots to UART serial console
+- a bcm2835-sdhci/mmc driver
+- pl011 UART
+```
+
 ### Custom
 
 If you have a customized ARM board, put it here.

mk/config.mk

@@ -21,6 +21,8 @@ REDOXFS_MKFS_FLAGS?=
 PODMAN_BUILD?=0
 ## The containerfile to use for the Podman base image
 CONTAINERFILE?=podman/redox-base-containerfile
+## Sub-device type for aarch64 if needed
+BOARD?=
 
 # Per host variables
 HOST_CARGO=env -u RUSTUP_TOOLCHAIN cargo
@@ -81,6 +83,7 @@ REPO_TAG=$(BUILD)/repo.tag
 endif
 
 FSTOOLS_TAG=build/fstools.tag
+export BOARD
 
 ## Cross compiler variables
 AR=$(TARGET)-gcc-ar