Allow to force min sdk given to Jack

Allows setting the min sdk version for target Jack commands,
overriding the default value obtained from LOCAL_SDK_CURRENT.

Bug: 28188420
Change-Id: I1b84ad8a7b6ae30639f8ade455c1e542af5692e4
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 7304bf8..7ee7ab3 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -112,6 +112,7 @@
 LOCAL_JILL_FLAGS:=
 LOCAL_CERTIFICATE:=
 LOCAL_SDK_VERSION:=
+LOCAL_MIN_SDK_VERSION:=
 LOCAL_SDK_RES_VERSION:=
 LOCAL_NDK_STL_VARIANT:=
 LOCAL_EMMA_INSTRUMENT:=