[flang][driver] Add support for `-fget-definition`

This patch adds `-fget-definition` to `flang-new`. The semantics of this
option are identical in both drivers. The error message in the
"throwaway" driver is updated so that it matches the one from
`flang-new` (which is auto-generated and cannot be changed easily).

Tests are updated accordingly. A dedicated test for error handling was
added: get-definition.f90 (for the sake of simplicity,
getdefinition01.f90 no longer tests for errors).

The `ParseFrontendArgs` function is updated so that it can return
errors. This change is required in order to report invalid values
following `-fget-definition`.

The actual implementation of `GetDefinitionAction::ExecuteAction()` was
extracted from f18.cpp (i.e. the bit that deals with
`-fget-definition`).

Depends on: https://reviews.llvm.org/D100556

Differential Revision: https://reviews.llvm.org/D100558

1 files changed, 3 insertions, 0 deletions

diff --git a/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp b/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
index 462de52..93bbf4f 100644
--- a/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
+++ b/flang/lib/FrontendTool/ExecuteCompilerInvocation.cpp
@@ -67,6 +67,9 @@ static std::unique_ptr<FrontendAction> CreateFrontendBaseAction(
   case DebugPreFIRTree:
     return std::make_unique<DebugPreFIRTreeAction>();
     break;
+  case GetDefinition:
+    return std::make_unique<GetDefinitionAction>();
+    break;
   case GetSymbolsSources:
     return std::make_unique<GetSymbolsSourcesAction>();
     break;