[llvm] big archive recognition by the llvm-symbolizer (PR #150401)

[James Henderson via llvm-commits]

================
@@ -535,16 +535,20 @@ MACH-O SPECIFIC OPTIONS
 .. option:: --default-arch <arch>
 
   If a binary contains object files for multiple architectures (e.g. it is a
-  Mach-O universal binary), symbolize the object file for a given architecture.
-  You can also specify the architecture by writing ``binary_name:arch_name`` in
-  the input (see example below). If the architecture is not specified in either
-  way, the address will not be symbolized. Defaults to empty string.
+  Mach-O universal binary or an AIX archive with architecture variants),
+  symbolize the object file for a given architecture. You can also specify
+  the architecture by writing ``binary_name:arch_name`` in the input (see
+  example below). For AIX archives, the format ``archive.a(member.o):arch``
+  is also supported. If the architecture is not specified in either way,
+  the address will not be symbolized. Defaults to empty string.
 
   .. code-block:: console
 
     $ cat addr.txt
     /tmp/mach_universal_binary:i386 0x1f84
     /tmp/mach_universal_binary:x86_64 0x100000f24
+    /tmp/archive.a(member.o):ppc 0x1000
+    /tmp/archive.a(member.o):ppc64 0x2000
----------------
jh7370 wrote:

```suggestion
    /tmp/big-archive.a(member.o):ppc 0x1000
    /tmp/big-archive.a(member.o):ppc64 0x2000
```
Let's do this to emphasise that it's the Big Archive format that is required in this case. It won't work with regular UNIX-style archives.

https://github.com/llvm/llvm-project/pull/150401