buildman: Update the default settings file

The settings file omits a few lines which are useful for getting every
board building. Add these and update the documentation tool.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/buildman/bsettings.py

@@ -79,10 +79,13 @@ other = /
 [toolchain-prefix]
 # name = path to prefix
 # e.g. x86 = /opt/gcc-4.6.3-nolibc/x86_64-linux/bin/x86_64-linux-
+# arc = /opt/arc/arc_gnu_2021.03_prebuilt_elf32_le_linux_install/bin/arc-elf32-
 
 [toolchain-alias]
 # arch = alias
 # Indicates which toolchain should be used to build for that arch
+riscv = riscv32
+sh = sh4
 x86 = i386
 blackfin = bfin
 openrisc = or1k

tools/buildman/buildman.rst

@@ -199,6 +199,8 @@ Setting up
    arc = /opt/arc/arc_gnu_2021.03_prebuilt_elf32_le_linux_install/bin/arc-elf32-
 
    [toolchain-alias]
+   riscv = riscv32
+   sh = sh4
    x86: i386
    blackfin: bfin
    openrisc: or1k