autotools: run ndk-build when 'make android' is invoked to simplify the build steps

Makefile.am

 
 PLATFORM=big_endian
 
-.PHONY: all clean distclean espeak-phoneme-data
+.PHONY: android all clean distclean espeak-phoneme-data
 
 EXTRA_DIST=
 
 espeak-data/phontab: src/espeakedit espeak-data/dictsource/dir.stamp espeak-data/phsource/dir.stamp
 	ESPEAK_DATA_PATH=$(PWD) src/espeakedit --compile
 
-##### android language data packs:
+##### android targets:
+
+jni:
+	cd android && ndk-build
 
 android/res/raw/espeakdata.zip: espeak-data/phontab dictionaries
 	mkdir -pv android/res/raw
 android/res/raw/espeakdata_version: android/res/raw/espeakdata.zip
 	sha1sum $< | awk '{ print $$1 }' > $@
 
-android: android/res/raw/espeakdata.zip android/res/raw/espeakdata_version
+android: \
+	jni \
+	android/res/raw/espeakdata.zip \
+	android/res/raw/espeakdata_version
 
 ##### dictionaries:
 

README.md

 
 ## Building eSpeak
 
-1.  Generate the build files and get the required git submodules by running:
+The eSpeak language data file and the JNI bindings needed for the Android
+APK can be build using the following commands:
 
-        $ ./autogen.sh
-1.  Build the `libttsespeak.so` file by running:
-
-        $ cd android
-        $ ndk-build
-2.  Build the `android/res/raw/espeakdata.zip` file by running:
-
-        $ ./configure --prefix=/usr
-        $ make android
+    $ ./autogen.sh
+    $ ./configure --prefix=/usr
+    $ make android
 
 ## Building the APK with Eclipse
 

configure.ac

 AC_PROG_MAKE_SET
 AC_PROG_LIBTOOL
 
+AC_CHECK_PROG(NDKBUILD_CHECK,[ndk-build],yes)
+if test x"$NDKBUILD_CHECK" != xyes ; then
+    AC_MSG_ERROR([Please ensure that the Android NDK is installed and ndk-build is usable from the command line.])
+fi
+
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