Unoptimal code with flags output and "asm goto"

The following testcase

```c
void foo (void);
void bar (void);

void qux (void)
{
_Bool err;

asm goto ("#" :"=@ccz" (err) : : : lab);

if (err)
bar ();

return;

lab:
if (err)
foo ();

return;
}
```

compiles with `clang -O2` to:

```asm
# %bb.0:
#APP
#
#NO_APP
sete %al
# %bb.1:
testb %al, %al
je .LBB0_4
# %bb.2:
jmp bar # TAILCALL
.LBB0_3: # Inline asm indirect target
# Label of block must be emitted
je foo # TAILCALL
.LBB0_4:
retq
```

Please note unnecessary `sete %al / testb %al,%al / je ...` sequence that could be substituted with simple `jne ...`, as is the case after .LBB0_3 inline asm indirect target label.

Start by reproducing the supplied C testcase with clang -O2 and comparing its assembly output. Trace the compiler handling of asm goto with an output flag and an indirect target; done means the redundant sete/testb/conditional-branch sequence is removed without changing either control-flow path.

Written by the indexing model from the issue text.