musl: doesn't support riscv32

musl doesn't support riscv32, so set COMPATIBLE_HOST appropriately.

(From OE-Core rev: c321d381cfecde6ec502317822eb4058cb3aced7)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/musl/musl.inc

@@ -25,6 +25,9 @@ MIPS_INSTRUCTION_SET = "mips"
 ARM_INSTRUCTION_SET:armv5 = "arm"
 ARM_INSTRUCTION_SET:armv4 = "arm"
 
+# 1.2.4 doesn't support riscv32
+COMPATIBLE_HOST:riscv32 = "null"
+
 # Enable out of tree build
 B = "${WORKDIR}/build"