Use ConstraintSemantics.getSupportedEnvironments() in supportsJava7TargetEnvironment

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MOS_MIGRATED_REVID=121150741

src/main/java/com/google/devtools/build/lib/analysis/constraints/EnvironmentCollection.java

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/constraints/EnvironmentCollection.java b/src/main/java/com/google/devtools/build/lib/analysis/constraints/EnvironmentCollection.java
index 160c87a..ad582f8 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/constraints/EnvironmentCollection.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/constraints/EnvironmentCollection.java
@@ -51,7 +51,7 @@
    * Returns the build labels of each environment in this collection, ordered by
    * their insertion order in {@link Builder}.
    */
-  ImmutableCollection<Label> getEnvironments() {
+  public ImmutableCollection<Label> getEnvironments() {
     return map.values();
   }