[flang][driver] Fix erroneous `&`

As pointed out by Valentin Clement in PR [1], we should be using `&&`
instead of `&`.

[1] https://github.com/flang-compiler/f18-llvm-project/pull/1113#discussion_r724321121

Differential Revision: https://reviews.llvm.org/D111395

GitOrigin-RevId: b41e86642e16dffc90d037449a59cded72b2bd7f
diff --git a/lib/Frontend/FrontendActions.cpp b/lib/Frontend/FrontendActions.cpp
index b43cf08..4dc0c2c 100644
--- a/lib/Frontend/FrontendActions.cpp
+++ b/lib/Frontend/FrontendActions.cpp
@@ -37,7 +37,7 @@
 }
 
 bool PrescanAndSemaAction::BeginSourceFileAction() {
-  return RunPrescan() & RunParse() && RunSemanticChecks();
+  return RunPrescan() && RunParse() && RunSemanticChecks();
 }
 
 //===----------------------------------------------------------------------===//