Pass --min-sdk-version to dx

Pass the sdk_version property, the platform sdk version, or 10000
to dx as --min-sdk-version.

Test: m -j checkbuild
Change-Id: I5fae03f44153dc2d6244c33f4c055e746980aefe

android/variable.go

@@ -108,6 +108,7 @@ type productVariables struct {
 	Make_suffix *string `json:",omitempty"`
 
 	Platform_sdk_version              *int     `json:",omitempty"`
+	Platform_sdk_final                *bool    `json:",omitempty"`
 	Platform_version_active_codenames []string `json:",omitempty"`
 	Platform_version_future_codenames []string `json:",omitempty"`