Use clang for android build

With androideabi-4.9, android build now supports threading.

android-config

@@ -39,8 +39,8 @@ PATH=$TOOLCHAIN/bin:$PATH
     --without-libxml2 \
     --disable-python-bindings \
     --disable-examples \
-    --disable-threads \
+    CC=clang \
+    CXX=clang++ \
     CPPFLAGS="-I$PREFIX/include" \
-    CXXFLAGS="-fno-strict-aliasing" \
     PKG_CONFIG_LIBDIR="$PREFIX/lib/pkgconfig" \
     LDFLAGS="-L$PREFIX/lib"

configure.ac

@@ -224,8 +224,8 @@ LIBS=$LIBS_OLD
 case "$host" in
   *android*)
     android_build=yes
-    # android does not need -pthread, but needs followng 2 libs for C++
-    APPLDFLAGS="$APPLDFLAGS -lstdc++ -lsupc++"
+    # android does not need -pthread, but needs followng 3 libs for C++
+    APPLDFLAGS="$APPLDFLAGS -lstdc++ -latomic -lsupc++"
     ;;
   *)
     PTHREAD_LDFLAGS="-pthread"

doc/sources/building-android-binary.rst

@@ -21,7 +21,9 @@ unpacked::
 
     $ build/tools/make-standalone-toolchain.sh \
       --install-dir=$ANDROID_HOME/toolchain \
-      --toolchain=arm-linux-androideabi-4.8
+      --toolchain=arm-linux-androideabi-4.9 \
+      --llvm-version=3.5 \
+      --platform=android-16
 
 The additional flag ``--system=linux-x86_64`` may be required if you
 are using x86_64 system.