[clang] Disable -fdollars-in-identifiers by default (PR #135407)

[Richard Smith via cfe-commits]

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@@ -119,7 +119,7 @@ LANGOPT(WChar             , 1, 0, "wchar_t keyword")
 LANGOPT(Char8             , 1, 0, "char8_t keyword")
 LANGOPT(IEEE128           , 1, 0, "__ieee128 keyword")
 LANGOPT(DeclSpecKeyword   , 1, 0, "__declspec keyword")
-BENIGN_LANGOPT(DollarIdents   , 1, 1, "'$' in identifiers")
+BENIGN_LANGOPT(DollarIdents   , 1, 0, "'$' in identifiers")
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zygoloid wrote:

Drive-by, but I think this should be a `COMPATIBLE_LANGOPT`, not a `BENIGN_LANGOPT`, since the same header built in the two different modes could generate different ASTs due to preprocessing differences.

https://github.com/llvm/llvm-project/pull/135407