build: proper support for android cross compilation

The build script needs to properly specify the target as android
so the gyp build scripts can properly leverage cross compilation
using the android NDK.

PR-URL: https://github.com/libuv/libuv/pull/433
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

android-configure

@@ -6,7 +6,7 @@ $1/build/tools/make-standalone-toolchain.sh \
     --toolchain=arm-linux-androideabi-4.8 \
     --arch=arm \
     --install-dir=$TOOLCHAIN \
-    --platform=android-9
+    --platform=android-21
 export PATH=$TOOLCHAIN/bin:$PATH
 export AR=arm-linux-androideabi-ar
 export CC=arm-linux-androideabi-gcc
@@ -16,5 +16,5 @@ export PLATFORM=android
 
 if [ $2 -a $2 == 'gyp' ]
   then
-    ./gyp_uv.py -Dtarget_arch=arm -DOS=android
+    ./gyp_uv.py -Dtarget_arch=arm -DOS=android -f make-android
 fi

common.gypi

@@ -35,7 +35,13 @@
         'xcode_settings': {
           'GCC_OPTIMIZATION_LEVEL': '0',
           'OTHER_CFLAGS': [ '-Wno-strict-aliasing' ],
-        }
+        },
+        'conditions': [
+          ['OS == "android"', {
+            'cflags': [ '-fPIE' ],
+            'ldflags': [ '-fPIE', '-pie' ]
+          }]
+        ]
       },
       'Release': {
         'defines': [ 'NDEBUG' ],