tools: idf_tools.py: allow macOS x86_64 tools to be installed on arm64

Until arm64 tool binaries are available, we can run existing x86_64
ones under emulation.

Suggested in https://github.com/espressif/esp-idf/issues/6113.

tools/idf_tools.py

@@ -121,6 +121,8 @@ PLATFORM_FROM_NAME = {
     'osx': PLATFORM_MACOS,
     'darwin': PLATFORM_MACOS,
     'Darwin-x86_64': PLATFORM_MACOS,
+    # pretend it is x86_64 until Darwin-arm64 tool builds are available:
+    'Darwin-arm64': PLATFORM_MACOS,
     # Linux
     PLATFORM_LINUX64: PLATFORM_LINUX64,
     'linux64': PLATFORM_LINUX64,