[clang] [DebugInfo] Add bit size to _BitInt name in debug info (PR #165583)

[Orlando Cazalet-Hyams via cfe-commits]

OCHyams wrote:

FWIW LLDB support seems limited currently as the type is printed as `short` and `a`'s value displayed as `32639` rather than `-129` (I don't think it's taking into account the DW_AT_bit_size here).
```c
$ cat test.c -n
     1  #include <string.h>
     2
     3  int main() {
     4    _BitInt(15) a;
     5    memset(&a, 0x7f, 2);
     6    return 0;     // GDB: b 6, p a
     7  }
```
```c
* thread #1, name = 'test.elf', stop reason = breakpoint 1.1
    frame #0: 0x0000555555555162 test.elf`main at test.c:6:3
   3    int main() {
   4      _BitInt(15) a;
   5      memset(&a, 0x7f, 2);
-> 6      return 0;     // GDB: b 6, p a
   7    }
(lldb) p a
(short) 32639
(lldb) im lookup -t _BitInt(15)
Best match found in /home/och/scratch/test.elf:
id = {0x00000042}, name = "_BitInt(15)", qualified = "short", byte-size = 2, compiler_type = "short"
```

If there's any LLDB testing I can do on my side please let me know



https://github.com/llvm/llvm-project/pull/165583