Add missing @AddToRuleKey annotations...

Summary: and comment on why some others aren't needed.

Test Plan: CI

Reviewed By: ttsugriy

fbshipit-source-id: d6320d9

src/com/facebook/buck/jvm/java/AbstractJavacPluginProperties.java

@@ -52,10 +52,13 @@ abstract class AbstractJavacPluginProperties implements AddsToRuleKey {
 
   public abstract ImmutableList<BuildRule> getClasspathDeps();
 
+  @AddToRuleKey
   public abstract boolean getCanReuseClassLoader();
 
+  @AddToRuleKey
   public abstract boolean getDoesNotAffectAbi();
 
+  @AddToRuleKey
   public abstract boolean getSupportsAbiGenerationFromSource();
 
   public boolean isEmpty() {

src/com/facebook/buck/jvm/java/ExternalOrJarBackedJavacProvider.java

@@ -34,8 +34,10 @@
 public class ExternalOrJarBackedJavacProvider implements JavacProvider, AddsToRuleKey {
   @AddToRuleKey private final SourcePath compiler;
   @AddToRuleKey @Nullable private final String compilerClassName;
+  @AddToRuleKey private Javac.Location javacLocation;
+
+  // This is just used to cache the Javac derived from the other fields.
   @Nullable private Javac javac;
-  private Javac.Location javacLocation;
 
   public ExternalOrJarBackedJavacProvider(
       SourcePath compiler, @Nullable String compilerClassName, Javac.Location javacLocation) {

src/com/facebook/buck/jvm/java/JarBackedJavacProvider.java

@@ -29,6 +29,8 @@ public class JarBackedJavacProvider implements JavacProvider, AddsToRuleKey {
   @AddToRuleKey private final SourcePath javacJarPath;
   @AddToRuleKey private final String compilerClassName;
   @AddToRuleKey private final Javac.Location javacLocation;
+
+  // This is just used to cache the Javac derived from the other fields.
   @Nullable private Javac javac;
 
   public JarBackedJavacProvider(