set GOOS=linux for the staticcheck tool

hack/verify-staticcheck.sh

@@ -94,7 +94,7 @@ while read -r error; do
   elif [[ "${in_failing}" -eq "0" ]]; then
     really_failing+=( "$pkg" )
   fi
-done < <(staticcheck -checks "${checks}" "${all_packages[@]}" 2>/dev/null || true)
+done < <(GOOS=linux staticcheck -checks "${checks}" "${all_packages[@]}" 2>/dev/null || true)
 
 export IFS=$'\n'  # Expand ${really_failing[*]} to separate lines
 kube::util::read-array really_failing < <(sort -u <<<"${really_failing[*]}")