Set min_sdk_version for SystemUISharedLib

Set min_sdk_version so that the manifest cant be merged into
Launcher3 when it is converted to Android.bp.

Test: mmma packages/apps/Launcher3
Change-Id: I28543d4be54aa789fbb452be005373239e1e0a6e
diff --git a/packages/SystemUI/shared/Android.bp b/packages/SystemUI/shared/Android.bp
index 31a538c..4471818 100644
--- a/packages/SystemUI/shared/Android.bp
+++ b/packages/SystemUI/shared/Android.bp
@@ -27,4 +27,6 @@
     // Enforce that the library is built against java 7 so that there are
     // no compatibility issues with launcher
     java_version: "1.7",
+
+    min_sdk_version: "26",
 }