[clang] Fix documentation on PGO/coverage related options. (PR #73845)

[Petr Hosek via cfe-commits]

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@@ -4401,13 +4413,18 @@ Execute ``clang-cl /?`` to see a list of supported options:
                               Instrument only functions from files where names don't match all the regexes separated by a semi-colon
       -fprofile-filter-files=<value>
                               Instrument only functions from files where names match any regex separated by a semi-colon
+      -fprofile-generate[=<dirname>]
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petrhosek wrote:

Rather than `<dirname>`, I think it'd be better to say `<pattern>` and point to https://clang.llvm.org/docs/UsersManual.html#profiling-with-instrumentation for more details.

https://github.com/llvm/llvm-project/pull/73845