mmake: -j$(nproc), passthrough o//

Now `mmake o/ape/ape.elf` works.

tool/zsh/mmake

@@ -23,9 +23,12 @@ esac
 }
 local -a targs
 local -a flags
+local j=-j$(autoload -Uz nproc >/dev/null 2>&1 ; nproc)
 while (( $# > 0 )); do
   case $1 in
+    -j*)    j=$1;         shift ;;
     -*|*=*) flags+=($1);  shift ;;
+    o/*)    flags+=($1);  shift ;;  # cheat; passthru
     *)      targs+=($1);  shift ;;
   esac
 done
@@ -33,4 +36,4 @@ local make
 [[ -x /opt/cosmocc/bin/make ]] && make=/opt/cosmocc/bin/make
 [[ -z $make ]] && make=build/bootstrap/make.com
 ( set -x
-  exec $make $flags MODE=$mode ${(@)targs/#/o/$mode/} )
+  exec $make $j $flags MODE=$mode ${(@)targs/#/o/$mode/} )

tool/zsh/nproc

@@ -0,0 +1,18 @@
+[[ -x $(whence -p nproc) ]] && {
+  command nproc && {
+    unfunction nproc
+    return
+  }
+}
+[[ -x $(which sysctl) ]] && {
+  nproc() {
+    sysctl -n hw.ncpu
+  }
+  nproc && return
+}
+# TODO other platforms
+echo nproc: no implementation found >&2
+nproc() {
+  echo 2
+}
+nproc