[llvm] [DebugInfo][NFC] Fix PDB/Native/LinePrinter.h build warning -Wmicrosoft-unqualified-friend (PR #209715)

[Wenju He via llvm-commits]

wenju-he wrote:

the warning is only observed on Windows debug build using icpx compiler (a downstream variant of clang).
```
[ 37%] Building CXX object lib/DebugInfo/LogicalView/CMakeFiles/LLVMDebugInfoLogicalView.dir/LVReaderHandler.cpp.obj
In file included from D:\netbatch\build_comp31108_00\ics_top\llvm\llvm\lib\DebugInfo\LogicalView\LVReaderHandler.cpp:15:
In file included from D:\netbatch\build_comp31108_00\ics_top\llvm\llvm\include\llvm\DebugInfo\LogicalView\Readers\LVCodeViewReader.h:23:
In file included from D:\netbatch\build_comp31108_00\ics_top\llvm\llvm\include\llvm\DebugInfo\LogicalView\Readers\LVCodeViewVisitor.h:40:
In file included from D:\netbatch\build_comp31108_00\ics_top\llvm\llvm\include\llvm\DebugInfo\PDB\Native\InputFile.h:17:
D:\netbatch\build_comp31108_00\ics_top\llvm\llvm\include\llvm\DebugInfo\PDB\Native\LinePrinter.h(52,16): error: unqualified friend declaration referring to type outside of the nearest enclosing namespace is a Microsoft extension; add a nested name specifier [-Werror,-Wmicrosoft-unqualified-friend]
   52 |   friend class WithColor;
      |                ^
      |                ::llvm::
1 error generated.
make[2]: *** [lib/DebugInfo/LogicalView/CMakeFiles/LLVMDebugInfoLogicalView.dir/build.make:257: lib/DebugInfo/LogicalView/CMakeFiles/LLVMDebugInfoLogicalView.dir/LVReaderHandler.cpp.obj] Error 1
make[1]: *** [CMakeFiles/Makefile2:28194: lib/DebugInfo/LogicalView/CMakeFiles/LLVMDebugInfoLogicalView.dir/all] Error 2
make: *** [Makefile:144: all] Error 2
```

https://github.com/llvm/llvm-project/pull/209715