wrk2: Mark incompatible with riscv32

It depends on luajit, which does not support riscv32.

Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-oe/recipes-benchmark/wrk2/wrk2_git.bb

@@ -45,4 +45,6 @@ do_install() {
     install -m 0755 wrk ${D}${bindir}/wrk2
     install -d ${D}${datadir}/wrk2
     install -m 0644 src/wrk.lua ${D}${datadir}/wrk2/wrk.lua
-}
+}
+
+COMPATIBLE_HOST:riscv32 = "null"