Add support for new pnacl native toolchain driver

ports/zlib/nacl.patch

 diff --git a/configure b/configure
 --- a/configure
 +++ b/configure
-@@ -188,6 +188,13 @@ if test "$gcc" -eq 1 && ($cc -c $test.c) >> configure.log 2>&1; then
+@@ -20,7 +20,11 @@ date >> configure.log
+ 
+ # set command prefix for cross-compilation
+ if [ -n "${CHOST}" ]; then
+-    uname="`echo "${CHOST}" | sed -e 's/^[^-]*-\([^-]*\)$/\1/' -e 's/^[^-]*-[^-]*-\([^-]*\)$/\1/' -e 's/^[^-]*-[^-]*-\([^-]*\)-.*$/\1/'`"
++    if [ "${CHOST}" = "le32-nacl" ]; then
++      uname="pnacl"
++    else
++      uname="`echo "${CHOST}" | sed -e 's/^[^-]*-\([^-]*\)$/\1/' -e 's/^[^-]*-[^-]*-\([^-]*\)$/\1/' -e 's/^[^-]*-[^-]*-\([^-]*\)-.*$/\1/'`"
++    fi
+     CROSS_PREFIX="${CHOST}-"
+ fi
+ 
+@@ -188,6 +192,13 @@ if test "$gcc" -eq 1 && ($cc -c $test.c) >> configure.log 2>&1; then
    *BSD | *bsd* | DragonFly)
          LDSHARED=${LDSHARED-"$cc -shared -Wl,-soname,libz.so.1,--version-script,zlib.map"}
          LDCONFIG="ldconfig -m" ;;
 +  pnacl)
 +        EXE='.pexe' ;;
 +  nacl)
 +        LDSHARED=${LDSHARED-"$cc -shared -Wl,-soname,libz.so.1,--version-script,zlib.map"}
 +        EXE='.nexe' ;;
 +  emscripten)
 +        EXE='.js' ;;
    CYGWIN* | Cygwin* | cygwin* | OS/2*)
          EXE='.exe' ;;
    MINGW* | mingw*)