[lldb] Fix remote macOS debugging on Apple Silicon

[JDevlieghere]

Summary

Update ARMGetSupportedArchitectureAtIndex to consider remote macOS
debugging. Currently, it defaults to an iOS triple when IsHost() returns
false. This fixes TestPlatformSDK.py on Apple Silicon.

[jasonmolenda]

Nice fix.

lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp

if (idx == 0) {
         arch = HostInfo::GetArchitecture(HostInfo::eArchKind32);
         return arch.IsValid();
       }
     }
   }
   return false;
 }
 
-// The architecture selection rules for arm processors These cpu subtypes have
-// distinct names (e.g. armv7f) but armv7 binaries run fine on an armv7f
-// processor.
-
+/// The architecture selection rules for arm processors These cpu subtypes have
+/// distinct names (e.g. armv7f) but armv7 binaries run fine on an armv7f
+/// processor.
 bool PlatformDarwin::ARMGetSupportedArchitectureAtIndex(uint32_t idx,
                                                         ArchSpec &arch) {
   ArchSpec system_arch(GetSystemArchitecture());
 
-// When lldb is running on a watch or tv, set the arch OS name appropriately.
 #if defined(TARGET_OS_TV) && TARGET_OS_TV == 1
 #define OSNAME "tvos"
 #elif defined(TARGET_OS_WATCH) && TARGET_OS_WATCH == 1
 #define OSNAME "watchos"
 #elif defined(TARGET_OS_BRIDGE) && TARGET_OS_BRIDGE == 1
 #define OSNAME "bridgeos"
+#elif defined(TARGET_OS_OSX) && TARGET_OS_OSX == 1
+#define OSNAME "macosx"
 #else
 #define OSNAME "ios"
 #endif
 
 #if TARGET_OS_OSX
   if (IsHost()) {
     if (idx == 0) {
       arch.SetTriple("arm64e-apple-macosx");