[clang] Handle tm mangling on Solaris in PPMacroExpansion.cpp (#100724)

The introduction of `std::put_time` in
fad17b4 broke the Solaris build:
```
Undefined			first referenced
 symbol  			    in file
_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_RSt8ios_basecPKSt2tmPKcSB_ lib/libclangLex.a(PPMacroExpansion.cpp.o)
ld: fatal: symbol referencing errors
```
As discussed in PR #99075, the problem is that GCC mangles `std::tm` as
`tm` on Solaris for binary compatility, while `clang` doesn't (Issue
#33114).

As a stop-gap measure, this patch introduces an `asm` level alias to the
same effect.

Tested on `sparcv9-sun-solaris2.11`, `amd64-pc-solaris2.11`, and
`x86_64-pc-linux-gnu`.

Author: rorth

clang/lib/Lex/PPMacroExpansion.cpp

@@ -1604,6 +1604,16 @@ static bool isTargetVariantEnvironment(const TargetInfo &TI,
   return false;
 }
 
+#if defined(__sun__) && defined(__svr4__)
+// GCC mangles std::tm as tm for binary compatibility on Solaris (Issue
+// #33114).  We need to match this to allow the std::put_time calls to link
+// (PR #99075).
+asm("_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
+    "RSt8ios_basecPKSt2tmPKcSB_ = "
+    "_ZNKSt8time_putIcSt19ostreambuf_iteratorIcSt11char_traitsIcEEE3putES3_"
+    "RSt8ios_basecPK2tmPKcSB_");
+#endif
+
 /// ExpandBuiltinMacro - If an identifier token is read that is to be expanded
 /// as a builtin macro, handle it and return the next token as 'Tok'.
 void Preprocessor::ExpandBuiltinMacro(Token &Tok) {