Replace dyn_cast with isa when the result isn't used (NFC)

Fix build warning: unused variable 'BB'

Author: joker-eph

llvm/lib/CodeGen/GlobalISel/InlineAsmLowering.cpp

@@ -264,7 +264,7 @@ bool InlineAsmLowering::lowerInlineAsm(
 
       OpInfo.CallOperandVal = const_cast<Value *>(Call.getArgOperand(ArgNo++));
 
-      if (const auto *BB = dyn_cast<BasicBlock>(OpInfo.CallOperandVal)) {
+      if (isa<BasicBlock>(OpInfo.CallOperandVal)) {
         LLVM_DEBUG(dbgs() << "Basic block input operands not supported yet\n");
         return false;
       }