Pass min sdk version to dx and desugar

Test: make checkbuild
Change-Id: Idde9712508571ea623126c7d25d2fa67eccf4833
diff --git a/core/definitions.mk b/core/definitions.mk
index e9ec26a..0be983a 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -2545,7 +2545,8 @@
 $(hide) java -jar $(DESUGAR) \
     $(addprefix --bootclasspath_entry ,$(call desugar-bootclasspath,$(PRIVATE_BOOTCLASSPATH))) \
     $(addprefix --classpath_entry ,$(PRIVATE_ALL_JAVA_LIBRARIES)) \
-    --min_sdk_version 24 --allow_empty_bootclasspath \
+    --min_sdk_version $(PRIVATE_SDK_VERSION) \
+    --allow_empty_bootclasspath \
     $(if $(filter --core-library,$(PRIVATE_DX_FLAGS)),--core_library) \
     -i $< -o $@.tmp
     mv $@.tmp $@
@@ -2561,6 +2562,7 @@
 $(hide) $(DX) \
     -JXms16M -JXmx2048M \
     --dex --output=$(dir $@) \
+    --min-sdk-version=$(PRIVATE_SDK_VERSION) \
     $(if $(NO_OPTIMIZE_DX), \
         --no-optimize) \
     $(if $(GENERATE_DEX_DEBUG), \