[llvm] [yaml2obj][MachO] Fix crash from integer underflow with invalid cmdsize (PR #165924)

[James Henderson via llvm-commits]

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@@ -37,7 +32,10 @@ LoadCommands:
     flags:           0
 ...
 
-## Test with an unknown load command value
+## Test with an unknown load command value.
+# RUN: yaml2obj %s --docnum=2 -o %t2 2>&1 | FileCheck %s --check-prefix=WARNING-UNKNOWN
+
+# WARNING-UNKNOWN: warning: load command 0 (0xdeadbeef) cmdsize too small (8 bytes) for actual size (20 bytes)
 --- !mach-o
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jh7370 wrote:

Nit: add a new line before the YAML.

https://github.com/llvm/llvm-project/pull/165924