All architectures may not support same set of tools, therefore use a
variable to specify this. E.g. on riscv32 rustfmt is not buildable
right now.
(From OE-Core rev: 332df9ebbd75a1825ac99abf1311d2e692d398d7)
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>