Kotlin/Java: Add compilation_info table

java/ql/lib/config/semmlecode.dbscheme

@@ -31,6 +31,12 @@ compilation_started(
     int id : @compilation ref
 )
 
+compilation_info(
+    int id : @compilation ref,
+    string info_key: string ref,
+    string info_value: string ref
+)
+
 /**
  * The arguments that were passed to the extractor for a compiler
  * invocation. If `id` is for the compiler invocation

java/ql/lib/semmle/code/java/Compilation.qll

@@ -143,4 +143,9 @@ class Compilation extends @compilation {
    * Holds if the extractor encountered non-recoverable errors.
    */
   predicate nonRecoverableErrors() { compilation_finished(this, _, _, 2) }
+
+  /**
+   * Gets the piece of compilation information with the given key, if any.
+   */
+  string getInfo(string key) { compilation_info(this, key, result) }
 }