[llvm] [llvm-objcopy][COFF] Update .symidx values after stripping (PR #153322)

[James Henderson via llvm-commits]

================
@@ -0,0 +1,225 @@
+## Bail out if a section consisting of symidx is invalid.
+## It includes both: an unexpected format for patching section data and
+## updating the checksum, as well as data validity.
+## Essentially, the expected format is a definitive symbol with a zero offset
+## linked to the section. Valid data consists of a sequence of symbol indices
+## that remain in the symbol table even after stripping.
+
+## In this case, the symbol .gfids$y is not present at all.
+
----------------
jh7370 wrote:

I'd delete this blank line, to make it clearer that the immediately preceding comment is tied to this specific set of RUN lines and not a general comment about the tests in the file. Same below for other case comments.

https://github.com/llvm/llvm-project/pull/153322