tracebox: Can't build on windows

minor ones:
```
/Fd"obj/src/tracebox/tracebox_c.pdb" /guard:cf /ZH:SHA_256
../../src/tracebox/tracebox.cc(125,7): error: use of undeclared identifier 'consumer_socket'
125 | consumer_socket = env;
| ^
../../src/tracebox/tracebox.cc(128,7): error: use of undeclared identifier 'producer_socket'
128 | producer_socket = env;
| ^
../../src/tracebox/tracebox.cc(130,49): error: use of undeclared identifier 'consumer_socket'
130 | base::SetEnv("PERFETTO_CONSUMER_SOCK_NAME", consumer_socket);
| ^
../../src/tracebox/tracebox.cc(131,49): error: use of undeclared identifier 'producer_socket'
131 | base::SetEnv("PERFETTO_PRODUCER_SOCK_NAME", producer_socket);
| ^
```

Need to look into more on:
```
[3/5] link tracebox.exe
FAILED: tracebox.exe
../../buildtools/win/clang/bin\lld-link.exe /nologo /guard:cf /DYNAMICBASE /OUT:./tracebox.exe /LIBPATH:"C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\ucrt\x64" /LIBPATH:"C:\Program Files (x86)\Windows Kits\10\Lib\10.0.22621.0\um\x64" /LIBPATH:"C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.37.32822\lib\x64" /DEBUG /PDB:./tracebox.exe.pdb @./tracebox.exe.rsp
lld-link: error: undefined symbol: int __cdecl perfetto::ProbesMain(int, char **)
>>> referenced by obj/src/tracebox/tracebox.tracebox.obj:(struct 0x8959D088::`anonymous namespace'::Applet const *const perfetto::`anonymous namespace'::g_applets)
ninja: build stopped: subcommand failed.
PS C:\Users\perfetto\perfetto>
```

Start with src/tracebox/tracebox.cc and reproduce the Windows build using the reported Ninja command. Trace the undeclared socket variables and the missing perfetto::ProbesMain symbol; done means tracebox.exe links successfully on Windows.

Written by the indexing model from the issue text.