C++: Make isMicrosoft() faster.

cpp/ql/src/semmle/code/cpp/File.qll

@@ -358,6 +358,11 @@ class File extends Container, @file {
   string getShortName() { files(underlyingElement(this), _, result, _, _) }
 }
 
+/**
+ * Holds if any file was compiled by a Microsoft compiler.
+ */
+cached predicate anyFileCompiledAsMicrosoft() { any(File f).compiledAsMicrosoft() }
+
 /**
  * A C/C++ header file, as determined (mainly) by file extension.
  *

cpp/ql/src/semmle/code/cpp/commons/Printf.qll

@@ -306,7 +306,7 @@ class FormatLiteral extends Literal {
    * Holds if this `FormatLiteral` is in a context that supports
    * Microsoft rules and extensions.
    */
-  predicate isMicrosoft() { any(File f).compiledAsMicrosoft() }
+  predicate isMicrosoft() { anyFileCompiledAsMicrosoft() }
 
   /**
    * Gets the format string, with '%%' and '%@' replaced by '_' (to avoid processing

cpp/ql/src/semmle/code/cpp/models/interfaces/FormattingFunction.qll

@@ -50,7 +50,7 @@ abstract class FormattingFunction extends ArrayFunction, TaintFunction {
    * Holds if this `FormattingFunction` is in a context that supports
    * Microsoft rules and extensions.
    */
-  predicate isMicrosoft() { any(File f).compiledAsMicrosoft() }
+  predicate isMicrosoft() { anyFileCompiledAsMicrosoft() }
 
   /**
    * Holds if the default meaning of `%s` is a `wchar_t *`, rather than