[clang] [Clang] Add fake use emission to Clang with -fextend-lifetimes (PR #110102)

[Zhengxing li via cfe-commits]

lizhengxing wrote:

It's a name mangling issue on Windows (or maybe other OS). 

For example, the check  `// CHECK-LABEL: define{{.*}}**_ZN1C4testEi**(ptr{{[^,]*}} %this, i32{{.*}} %p)` in fake-use-this.cpp expects the string contains `_ZN1C4testEi`. 

However, the compiler on Windows outputs `define dso_local noundef zeroext i1 @"?test at C@@QEAA_NH at Z"` 


https://github.com/llvm/llvm-project/pull/110102