[clang] [clang][analysis] Fix flaky clang/test/Analysis/live-stmts.cpp test (PR #126913)

[Mikael Holmén via cfe-commits]

mikaelholmen wrote:

Unfortunately the test still seems to be flaky. With EXPENSIVE_CHECKS I often see it fail on the RHEL8 x86_64 machines I use.
E.g.
```
FAIL: Clang :: Analysis/live-stmts.cpp (1 of 1)
******************** TEST 'Clang :: Analysis/live-stmts.cpp' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 1: /repo/uabelho/main-github/llvm/build-all-expensive/bin/clang -cc1 -internal-isystem /repo/uabelho/main-github/llvm/build-all-expensive/lib/clang/21/include -nostdsysteminc -analyze -analyzer-constraints=range -setup-static-analyzer -w -analyzer-checker=debug.DumpLiveExprs /repo/uabelho/main-github/clang/test/Analysis/live-stmts.cpp 2>&1   | /repo/uabelho/main-github/llvm/build-all-expensive/bin/FileCheck /repo/uabelho/main-github/clang/test/Analysis/live-stmts.cpp
+ /repo/uabelho/main-github/llvm/build-all-expensive/bin/clang -cc1 -internal-isystem /repo/uabelho/main-github/llvm/build-all-expensive/lib/clang/21/include -nostdsysteminc -analyze -analyzer-constraints=range -setup-static-analyzer -w -analyzer-checker=debug.DumpLiveExprs /repo/uabelho/main-github/clang/test/Analysis/live-stmts.cpp
+ /repo/uabelho/main-github/llvm/build-all-expensive/bin/FileCheck /repo/uabelho/main-github/clang/test/Analysis/live-stmts.cpp
/repo/uabelho/main-github/clang/test/Analysis/live-stmts.cpp:227:16: error: CHECK-EMPTY: is not on the line after the previous match
// CHECK-EMPTY:
               ^
<stdin>:160:1: note: 'next' match was here

^
<stdin>:157:81: note: previous match ended here
| `-DeclRefExpr 0x55e1600cec58 '_Bool' lvalue ParmVar 0x55e1600cead8 'b' '_Bool'
                                                                                ^
<stdin>:158:1: note: non-matching line after previous match is here
`-ImplicitCastExpr 0x55e1600cecb0 '_Bool' <LValueToRValue>
^

Input file: <stdin>
Check file: /repo/uabelho/main-github/clang/test/Analysis/live-stmts.cpp

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           .
           .
           .
         155: BinaryOperator 0x55e1600cecc8 '_Bool' '||' 
         156: |-ImplicitCastExpr 0x55e1600cec98 '_Bool' <LValueToRValue> 
         157: | `-DeclRefExpr 0x55e1600cec58 '_Bool' lvalue ParmVar 0x55e1600cead8 'b' '_Bool' 
         158: `-ImplicitCastExpr 0x55e1600cecb0 '_Bool' <LValueToRValue> 
         159:  `-DeclRefExpr 0x55e1600cec78 '_Bool' lvalue ParmVar 0x55e1600cead8 'b' '_Bool' 
         160:  
empty:227     ! error: match on wrong line
         161: ImplicitCastExpr 0x55e1600cec98 '_Bool' <LValueToRValue> 
         162: `-DeclRefExpr 0x55e1600cec58 '_Bool' lvalue ParmVar 0x55e1600cead8 'b' '_Bool' 
         163:  
         164: ImplicitCastExpr 0x55e1600cecb0 '_Bool' <LValueToRValue> 
         165: `-DeclRefExpr 0x55e1600cec78 '_Bool' lvalue ParmVar 0x55e1600cead8 'b' '_Bool' 
           .
           .
           .
>>>>>>

--

********************
********************
Failed Tests (1):
  Clang :: Analysis/live-stmts.cpp
```

https://github.com/llvm/llvm-project/pull/126913