[clang] [clang] Document -fstrict-flex-arrays option (PR #138388)

[Richard Smith via cfe-commits]

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@@ -1554,7 +1554,10 @@ def fstrict_flex_arrays_EQ : Joined<["-"], "fstrict-flex-arrays=">, Group<f_Grou
   Visibility<[ClangOption, CC1Option]>,
   NormalizedValuesScope<"LangOptions::StrictFlexArraysLevelKind">,
   NormalizedValues<["Default", "OneZeroOrIncomplete", "ZeroOrIncomplete", "IncompleteOnly"]>,
-  HelpText<"Enable optimizations based on the strict definition of flexible arrays">,
+  HelpText<"Enable optimizations based on the strict definition of flexible arrays. "
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zygoloid wrote:

This is much too long to include in the `--help` output. Maybe this could be specified as `DocBrief` instead soon it goes into the command-line reference but not `--help`

https://github.com/llvm/llvm-project/pull/138388