Unexpected `-std=c2y` octal warnings on zero with type suffix

[dzaima]

The C code long long foo = 0ll;, compiled with -std=c2y, gives:

<source>:1:17: warning: octal literals without a '0o' prefix are deprecated [-Wdeprecated-octal-literals]
    1 | long long foo = 0ll;
      |                 ^

but should not. (same with 0u, 0l, 0ul, 0ull)

https://godbolt.org/z/YKoWs9brM
(from a discussion on Discord)

[markmi]

For Reference:
The N3550 full language draft classifies the old notation under: “Certain features are obsolescent, which means that they could be considered for withdrawal in future revisions of this document. They are retained because of their widespread use, . . .”