Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I080090d50f1a368a4e7c1a0732297bb6a295e34f
diff --git a/tools/aapt/Command.cpp b/tools/aapt/Command.cpp
index 9976d00..447ace6 100644
--- a/tools/aapt/Command.cpp
+++ b/tools/aapt/Command.cpp
@@ -494,7 +494,7 @@
 
 struct Feature {
     Feature() : required(false), version(-1) {}
-    Feature(bool required, int32_t version = -1) : required(required), version(version) {}
+    explicit Feature(bool required, int32_t version = -1) : required(required), version(version) {}
 
     /**
      * Whether the feature is required.