Add functions to provide target sdk version

Bug: http://b/21364029
Change-Id: I8648d1bff6c8fd6e7cd12da7f128e048b9f2829a
diff --git a/linker/Android.mk b/linker/Android.mk
index 4a7da76..00add7d 100644
--- a/linker/Android.mk
+++ b/linker/Android.mk
@@ -7,6 +7,7 @@
     dlfcn.cpp \
     linker.cpp \
     linker_allocator.cpp \
+    linker_sdk_versions.cpp \
     linker_block_allocator.cpp \
     linker_environ.cpp \
     linker_libc_support.c \