[llvm] Aggregate errors from llvm-dwarfutil --verify (PR #79648)

[Kevin Frei via llvm-commits]

================
@@ -50,7 +50,11 @@
 # CHECK-NEXT:               DW_AT_decl_line   [DW_FORM_sdata] (3)
 # CHECK-NEXT:               DW_AT_call_file   [DW_FORM_sdata] (4)
 # CHECK-NEXT:               DW_AT_call_line   [DW_FORM_sdata] (5){{[[:space:]]}}
-
+# CHECK-NEXT: Verifying dwo Units...
+# CHECK-NEXT: error: Aggregated error category counts:
+# CHECK-NEXT: error: Error category 'Invalid encoding in DW_AT_decl_file' occurred 4 time(s).
----------------
kevinfrei wrote:

This was where I just threw something together, because I assumed whatever I did would require revisiting :) 
```
error: <Error summary? Aggregated issues? Not sure what's best for the header>:
error: Invalid encoding in DW_AT_decl-file was reported 4 times(s).
error: ....
```
seems better (and less redundant)

https://github.com/llvm/llvm-project/pull/79648