android: set ASFLAGS as well as CFLAGS.

Cherrypick of upstream gyp r1857:

The Android build system doesn't use CFLAGS for assembly source files,
but gyp expects this. Set LOCAL_ASFLAGS in gyp-generated targets to the
same as LOCAL_CFLAGS.

Change-Id: Iec84bdb3807fa9b4469f16d31ef372644a0a2804
diff --git a/pylib/gyp/generator/android.py b/pylib/gyp/generator/android.py
index 1d8a21c..7983fb6 100644
--- a/pylib/gyp/generator/android.py
+++ b/pylib/gyp/generator/android.py
@@ -501,6 +501,9 @@
     self.WriteLn('LOCAL_C_INCLUDES := $(GYP_COPIED_SOURCE_ORIGIN_DIRS) '
                                      '$(LOCAL_C_INCLUDES_$(GYP_CONFIGURATION))')
     self.WriteLn('LOCAL_CPPFLAGS := $(LOCAL_CPPFLAGS_$(GYP_CONFIGURATION))')
+    # Android uses separate flags for assembly file invocations, but gyp expects
+    # the same CFLAGS to be applied:
+    self.WriteLn('LOCAL_ASFLAGS := $(LOCAL_CFLAGS)')
 
 
   def WriteSources(self, spec, configs, extra_sources):