SDK: Also read sdk/build/tools.OS.atree

This allows us to have per-host OS (or OS + arch) atree files in case we
need to get tools which source varies per host OS, example:
- sdk/build/tools.linux.atree
- sdk/build/tools.linux-x86_64.atree
- sdk/build/tools.windows.atree
etc.

Change-Id: I9a1256548345fb866b0750fce6810913413dd946
diff --git a/core/Makefile b/core/Makefile
index 819eb38..8d0dfed 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -1382,6 +1382,12 @@
 ifneq (,$(strip $(wildcard sdk/build/tools.$(TARGET_ARCH).atree)))
   sdk_tools_atree_files += sdk/build/tools.$(TARGET_ARCH).atree
 endif
+ifneq (,$(strip $(wildcard sdk/build/tools.$(HOST_OS).atree)))
+  sdk_tools_atree_files += sdk/build/tools.$(HOST_OS).atree
+endif
+ifneq (,$(strip $(wildcard sdk/build/tools.$(HOST_OS)-$(HOST_ARCH).atree)))
+  sdk_tools_atree_files += sdk/build/tools.$(HOST_OS)-$(HOST_ARCH).atree
+endif
 
 sdk_atree_files := \
 	$(atree_dir)/sdk.exclude.atree \