Switch to SDK_HOST_ARCH

SDK_HOST_ARCH will be x86 if we are doing 32-bit host multilib build,
in which HOST_ARCH is actually x86_64.

Bug: 13751317
Change-Id: I8b7893b10cc4d0e71076b3b3625ec2f352aa8602
diff --git a/tools/elftree/Android.mk b/tools/elftree/Android.mk
index b1c1eb7..5f2849d 100644
--- a/tools/elftree/Android.mk
+++ b/tools/elftree/Android.mk
@@ -14,8 +14,8 @@
 
 LOCAL_PATH := $(call my-dir)
 
-supported_platforms := linux-x86
-cur_platform := $(filter $(HOST_OS)-$(HOST_ARCH),$(supported_platforms))
+supported_platforms := linux
+cur_platform := $(filter $(HOST_OS),$(supported_platforms))
 
 ifdef cur_platform