Compile with android NDK r10b 32bit target

Android does not have _Exit.  We detect this and use _exit instead.
clang-3.4 has an issue around undefined reference to
__atomic_fetch_add_4, so we stick to gcc-4.8 for now.

android-config

@@ -40,8 +40,6 @@ PATH=$TOOLCHAIN/bin:$PATH
     --disable-python-bindings \
     --disable-examples \
     --disable-threads \
-    CC=arm-linux-androideabi-clang \
-    CXX=arm-linux-androideabi-clang++ \
     CPPFLAGS="-I$PREFIX/include" \
     PKG_CONFIG_LIBDIR="$PREFIX/lib/pkgconfig" \
     LDFLAGS="-L$PREFIX/lib"

configure.ac

@@ -437,6 +437,7 @@ if test "x$cross_compiling" != "xyes"; then
   AC_FUNC_MALLOC
 fi
 AC_CHECK_FUNCS([ \
+  _Exit \
   getpwnam \
   memmove \
   memset \

doc/sources/building-android-binary.rst

@@ -16,8 +16,7 @@ unpacked::
 
     $ build/tools/make-standalone-toolchain.sh \
       --install-dir=$ANDROID_HOME/toolchain \
-      --toolchain=arm-linux-androideabi-4.8 \
-      --llvm-version=3.4
+      --toolchain=arm-linux-androideabi-4.8
 
 The additional flag ``--system=linux-x86_64`` may be required if you
 are using x86_64 system.

src/shrpx.h

@@ -44,6 +44,10 @@
 #define SOCK_CLOEXEC 0
 #endif // !SOCK_CLOEXEC
 
+#ifndef HAVE__EXIT
+#define _Exit(status) _exit(status)
+#endif // !HAVE__EXIT
+
 #define DIE()                                   \
   assert(0);