android: add libecl build instructions

INSTALL

@@ -1,22 +1,62 @@
 You will find detailed installation instructions in the ECL manual
-       http://ecls.sourceforge.net/new-manual/pr01s06.html
-If you do not have access to the online version, follow the following two small recipies.
+       https://common-lisp.net/project/ecl/manual/pr01s06.html
+If you do not have access to the online version, follow the following recipies.
 
 * Unix and similar platforms.
-   1. Type
-       ./configure --help
-      to get a list of the flags with which ECL can be configured.
-   2. Enter
-       ./configure ...
-      where "..." is the set of flags you have chosen.
-   3. Use "make" followed by "make install" to build and install ECL.
+  1. Type
+     ./configure --help
+     to get a list of the flags with which ECL can be configured.
+  2. Enter
+     ./configure ...
+     where "..." is the set of flags you have chosen.
+  3. Use "make" followed by "make install" to build and install ECL.
 
 * Windows with Visual Studio C++ 2008
-   1. Enter the msvc directory
-   2. Read the file Makefile to find the configuration options. They typically have the
-      form ECL_UNICODE=1, ECL_THREADS=1, etc
-   3. Enter
-       nmake ...
-      followed by zero or more of those options
-   4. Use "nmake install" to create a directory called "package" with ECL in it.
-   5. Move that directory wherever you need.
+  1. Enter the msvc directory
+  2. Read the file Makefile to find the configuration options. They typically have the
+     form ECL_UNICODE=1, ECL_THREADS=1, etc
+  3. Enter
+     nmake ...
+     followed by zero or more of those options
+  4. Use "nmake install" to create a directory called "package" with ECL in it.
+  5. Move that directory wherever you need.
+
+* Cross-compile for the android platform (from the UNIX machine)
+  1. Build the host ECL
+     #+BEGIN_SRC shell-script
+     ./configure ABI=32 CFLAGS="-m32 -g -O2" LDFLAGS="-m32 -g -O2" \
+            --prefix=`pwd`/ecl-android-host \
+            --disable-longdouble \
+            --enable-libatomic=included
+     make -j9
+     make install
+     rm -r build
+     export ECL_TO_RUN=`pwd`/ecl-android-host/bin/ecl
+     #+END_SRC
+  2. Build the toolchain (requires android-ndk) and export the
+     necessary paths - if you have a toolchain for the android just
+     export it's bin/ directory
+     #+BEGIN_SRC shell-script
+       export PLATFORM_PREFIX=/opt/toolchains/android-ndk/
+       export NDK_PATH=/opt/android-ndk/
+       export NDK_PLATFORM=android-4
+
+       mkdir ${PLATFORM_PREFIX}
+       ${NDK_PATH}/build/tools/make-standalone-toolchain.sh \
+                  --platform=${NDK_PLATFORM} \
+                  --install-dir=${PLATFORM_PREFIX} \
+                  --arch=arm
+
+       export PATH=${PLATFORM_PREFIX}/bin:${PATH}
+    #+END_SRC
+  3. Build and install the target library
+     #+BEGIN_SRC shell-script
+       ./configure --host=arm-linux-androideabi \
+                   --prefix=`pwd`/ecl-android \
+                   --with-cross-config=`pwd`/android.cross_config \
+                   --disable-soname
+       make -j9
+       make install
+     #+END_SRC
+  4. Library and assets in the ecl-android directory are ready to run
+     on the Android system.

android.cross_config

@@ -0,0 +1,21 @@
+CL_FIXNUM_TYPE=int
+CL_FIXNUM_BITS=32
+CL_FIXNUM_MAX=536870911L
+CL_FIXNUM_MIN=-536870912L
+CL_INT_BITS=32
+CL_LONG_BITS=32
+ECL_STACK_DIR=down
+ECL_BIGENDIAN=no
+ECL_NEWLINE=LF
+ECL_FILE_CNT=2
+ECL_STDINT_HEADER="#include <stdint.h>"
+ECL_UINT8_T=uint8_t
+ECL_UINT16_T=uint16_t
+ECL_UINT32_T=uint32_t
+ECL_UINT64_T=no
+ECL_INT8_T=int8_t
+ECL_INT16_T=int16_t
+ECL_INT32_T=int32_t
+ECL_INT64_T=no
+ECL_LONG_LONG_BITS=no
+ECL_WORKING_ENVIRON=yes