Don't emit a bunch of spurious "Unknown platform 0" warnings from debugserver

[jingham]

Summary

The code that was trying to get the platform string was passing the MachProcess::DeploymentInfo.platform to GetPlatformString w/o checking first whether that load command actually provided a platform number. DeploymentInfo already had a bool operator that checked if the platform had been set, so just check that first before calling GetPlatformString. NFC except a little less spam in the debugserver log output.

[jasonmolenda]

Ah good catch, thanks.

lldb/tools/debugserver/source/DNB.cpp

if (GetProcessSP(pid, procSP)) {
     // macOS binary) is loaded with the macCatalyst dyld platform
     // override. The image info corrects for this, but qProcessInfo
     // will return what is in the binary.
     auto info =
         procSP->GetDeploymentInfo(lc, load_command_address, is_executable);
     major_version = info.major_version;
     minor_version = info.minor_version;
     patch_version = info.patch_version;
+    // MachProcess::DeploymentInfo has a bool operator to tell whether we have
+    // set the platform.  If that's not true, don't report out the platform:
+    if (!info)
+      return {};
     return procSP->GetPlatformString(info.platform);
   }
-  return nullptr;
+  return {};
 }
 
 // Get the current shared library information for a process. Only return
 // the shared libraries that have changed since the last shared library
 // state changed event if only_changed is non-zero.
 nub_size_t
 DNBProcessGetSharedLibraryInfo(nub_process_t pid, nub_bool_t only_changed,
                                struct DNBExecutableImageInfo **image_infos) {