[NFC][offloader] Mark run() definition static to match its declaration (#1250)

Minor nit: `run()` in `tools/offloader/offloader.cpp` is
forward-declared `static` but the definition omits the specifier. Adding
it matches the other two helpers in this file and the readability
rationale in the [LLVM Coding
Standards](https://llvm.org/docs/CodingStandards.html#restrict-visibility).
NFC.

Assisted by Claude Opus 4.7.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: alsepkow

tools/offloader/offloader.cpp

@@ -96,7 +96,7 @@ static bool matchesRegexIgnoreCase(StringRef GPUDescription,
   return R.isValid() && R.match(GPUDescription);
 }
 
-int run() {
+static int run() {
   const ExitOnError ExitOnErr("gpu-exec: error: ");
   const DeviceConfig Config = {Debug, Validation};
   auto DevicesOrErr = initializeDevices(Config);