Some NDK build info updated.

src/frontends/android/README.ndk

@@ -3,7 +3,9 @@ folder:
 
  - strongswan: The strongSwan sources.  This can either be an extracted tarball,
    or a symlink to the Git repository.  To build from the repository the sources
-   have to be prepared first: ./autogen && ./configure && make && make distclean
+   have to be prepared first (see HACKING for a list of required tools):
+
+     ./autogen.sh && ./configure && make && make distclean
 
  - openssl: The OpenSSL sources.  Since the sources need to be changed to be
    built on Android (and especially in the NDK), we provide a modified mirror
@@ -11,9 +13,10 @@ folder:
 
  - vstr: The Vstr string library.  Since cross-compiling this library is not
    that easy with the configure script and Makefiles included in the tarball,
-   the easiest way to build it is still to use droid-gcc (as described on
-   wiki.strongswan.org).  The build script provided on the wiki builds the
-   library and copies the required header files to the configured installation
+   the easiest way to build it is using either droid-gcc (as described on
+   wiki.strongswan.org) or a standalone toolchain built with the NDK.
+   The build script provided on the wiki builds the library with droid-gcc
+   and copies the required header files to the configured installation
    directory.  Please note that the Android.mk provided on the wiki (vstr.mk)
    does not work in the NDK.  A replacement is already in place in jni/vstr.