Add emscripten support to config.sub

ports/zlib/nacl.patch

Index: ports/zlib/nacl.patch
diff --git a/ports/zlib/nacl.patch b/ports/zlib/nacl.patch
index 480a7462464852690376b2d0e250704b6ff52f33..720f3b8766959025c34d20ac45225c799038ade1 100644
--- a/ports/zlib/nacl.patch
+++ b/ports/zlib/nacl.patch
@@ -1,18 +1,16 @@
 diff --git a/configure b/configure
 --- a/configure
 +++ b/configure
-@@ -188,6 +188,15 @@ if test "$gcc" -eq 1 && ($cc -c $test.c) >> configure.log 2>&1; then
+@@ -188,6 +188,13 @@ if test "$gcc" -eq 1 && ($cc -c $test.c) >> configure.log 2>&1; then
    *BSD | *bsd* | DragonFly)
          LDSHARED=${LDSHARED-"$cc -shared -Wl,-soname,libz.so.1,--version-script,zlib.map"}
          LDCONFIG="ldconfig -m" ;;
 +  pnacl)
-+        LDSHARED=${LDSHARED-"$cc -shared -Wl,-soname,libz.so.1,--version-script,zlib.map"}
 +        EXE='.pexe' ;;
 +  nacl)
 +        LDSHARED=${LDSHARED-"$cc -shared -Wl,-soname,libz.so.1,--version-script,zlib.map"}
 +        EXE='.nexe' ;;
-+  em)
-+        LDSHARED=${LDSHARED-"$cc -shared -Wl,-soname,libz.so.1,--version-script,zlib.map"}
++  emscripten)
 +        EXE='.js' ;;
    CYGWIN* | Cygwin* | cygwin* | OS/2*)
          EXE='.exe' ;;