Fix formatMethod() when all arguments are named

Previously an error might look like:

  Type PackagingCommon has no function directory(Label labelstring pathint mode).

Now, it shows up correctly as:

  Type PackagingCommon has no function directory(Label label, string path, int mode).

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MOS_MIGRATED_REVID=133285688

src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
index 5c8f13a..49f85f0 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/FuncallExpression.java
@@ -505,6 +505,7 @@
       sb.append(EvalUtils.getDataTypeName(kwarg.getValue()));
       sb.append(" ");
       sb.append(kwarg.getKey());
+      first = false;
     }
     return sb.append(")").toString();
   }