Add option to force filetype=asm for testing

tests_lit/llvm2ice_tests/loop-nest-depth.ll

 ; Test the the loop nest depth is correctly calculated for basic blocks.
 
 ; REQUIRES: allow_dump
 
-; Single threaded so that the dumps used for checking happen in order
+; Single threaded so that the dumps used for checking happen in order.
 ; RUN: %p2i --filetype=obj --disassemble -i %s --args -O2 --verbose=loop \
-; RUN: --threads=0 | FileCheck %s
+; RUN:     -log=%t --threads=0 && FileCheck %s < %t
 
 define internal void @test_single_loop(i32 %a32) {
 entry:
   %a = trunc i32 %a32 to i1
   br label %loop0
 
 loop0:                               ; <-+
   br label %loop1                    ;   |
 loop1:                               ;   |
   br i1 %a, label %loop0, label %out ; --+
@@ skipping 279 matching lines @@
 }
 
 ; CHECK-LABEL: After loop nest depth analysis
 ; CHECK-NEXT: entry:
 ; CHECK-NEXT: LoopNestDepth = 0
 ; CHECK-NEXT: body:
 ; CHECK-NEXT: LoopNestDepth = 1
 ; CHECK-NEXT: exit:
 ; CHECK-NEXT: LoopNestDepth = 0
 ; CHECK-LABEL: Before RMW