Fix build by removing libportable from the default build.

Easier than working out how to fix the fenv stuf...

Change-Id: Id457d4fcd790b1fc13047cba29c7d47118196a87
diff --git a/ndk/sources/android/libportable/Android.mk b/ndk/sources/android/libportable/Android.mk
index 1ad8440..6c52e89 100644
--- a/ndk/sources/android/libportable/Android.mk
+++ b/ndk/sources/android/libportable/Android.mk
@@ -16,6 +16,8 @@
 
 LOCAL_PATH := $(call my-dir)
 
+ifeq ($(BUILD_LIBPORTABLE_TOO),true)
+
 #=====================================================================
 # Device Shared Library libportable
 #=====================================================================
@@ -42,3 +44,5 @@
 LOCAL_SHARED_LIBRARIES += liblog libdl
 
 include $(BUILD_SHARED_LIBRARY)
+
+endif # BUILD_LIBPORTABLE_TOO