Switch mips64 back to NDK r10.

The NDK doesn't support mips32r6, and the update of prebuilts/ndk to
r11 doesn't have the hack that r10 did. Revert back to r10, until we
decide on a more appropriate solution.

Change-Id: I7891603d8ccbb20398aad893b62c1debf353ef41
diff --git a/core/binary.mk b/core/binary.mk
index c017e70..0c6d8e8 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -69,6 +69,18 @@
   ifdef LOCAL_IS_HOST_MODULE
     $(error $(LOCAL_PATH): LOCAL_SDK_VERSION cannot be used in host module)
   endif
+
+  # mips32r6 is not supported by the NDK. No released NDK contains these
+  # libraries, but the r10 in prebuilts/ndk had a local hack to add them :(
+  #
+  # We need to find a real solution to this problem, but until we do just drop
+  # mips32r6 things back to r10 to get the tree building again.
+  ifeq (mips32r6,$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH_VARIANT))
+    ifeq ($(LOCAL_NDK_VERSION), current)
+      LOCAL_NDK_VERSION := r10
+    endif
+  endif
+
   my_ndk_source_root := $(HISTORICAL_NDK_VERSIONS_ROOT)/$(LOCAL_NDK_VERSION)/sources
   my_ndk_sysroot := $(HISTORICAL_NDK_VERSIONS_ROOT)/$(LOCAL_NDK_VERSION)/platforms/android-$(LOCAL_SDK_VERSION)/arch-$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH)
   my_ndk_sysroot_include := $(my_ndk_sysroot)/usr/include
@@ -109,6 +121,9 @@
   my_ndk_stl_static_lib :=
   my_ndk_stl_cppflags :=
   my_cpu_variant := $(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)CPU_ABI)
+  ifeq (mips32r6,$(TARGET_$(LOCAL_2ND_ARCH_VAR_PREFIX)ARCH_VARIANT))
+    my_cpu_variant := mips32r6
+  endif
   LOCAL_NDK_STL_VARIANT := $(strip $(LOCAL_NDK_STL_VARIANT))
   ifeq (,$(LOCAL_NDK_STL_VARIANT))
     LOCAL_NDK_STL_VARIANT := system