[Flang][bbc] Prevent bbc -emit-fir command invoking all passes twice

Currently when the bbc tool is invoked with the emit-fir command the pass pipeline will be invoked twice causing passes added to the pass manager to
run twice on the input IR.

This change seeks to prevent that from occuring by only invoking the pass
managers run command once and situationally adding the HLFIR to FIR
pass pipeline in the same scenario as before.

Author: agozillon

flang/tools/bbc/bbc.cpp

@@ -389,18 +389,14 @@ static mlir::LogicalResult convertFortranSourceToMLIR(
     // --emit-fir: Build the IR, verify it, and dump the IR if the IR passes
     // verification. Use --dump-module-on-failure to dump invalid IR.
     pm.addPass(std::make_unique<Fortran::lower::VerifierPass>());
-    if (mlir::failed(pm.run(mlirModule))) {
-      llvm::errs() << "FATAL: verification of lowering to FIR failed";
-      return mlir::failure();
-    }
 
-    if (emitFIR && useHLFIR) {
-      // lower HLFIR to FIR
+    // Add HLFIR to FIR lowering pass
+    if (emitFIR && useHLFIR)
       fir::createHLFIRToFIRPassPipeline(pm, llvm::OptimizationLevel::O2);
-      if (mlir::failed(pm.run(mlirModule))) {
-        llvm::errs() << "FATAL: lowering from HLFIR to FIR failed";
-        return mlir::failure();
-      }
+
+    if (mlir::failed(pm.run(mlirModule))) {
+      llvm::errs() << "FATAL: verification of FIR or HLFIR module failed";
+      return mlir::failure();
     }
 
     printModule(mlirModule, out);