tools: add CMake for linux-arm64 (aarch64) platform

Allows installing cmake on aarch64 linux platforms. Also necessary
when building IDF docker image on macOS aarch64.

Part of https://github.com/espressif/esp-idf/issues/6432

tools/tools.json

@@ -475,6 +475,11 @@
             "size": 43877847,
             "url": "https://github.com/Kitware/CMake/releases/download/v3.20.3/cmake-3.20.3-linux-x86_64.tar.gz"
           },
+          "linux-arm64": {
+            "sha256": "77620f99e9d5f39cf4a49294c6a68c89a978ecef144894618974b9958efe3c2a",
+            "size": 45139836,
+            "url": "https://github.com/Kitware/CMake/releases/download/v3.20.3/cmake-3.20.3-linux-aarch64.tar.gz"
+          },
           "linux-armel": {
             "sha256": "f8bd050c2745f0dcc4b7cef9738bbfef775950a10f5bd377abb0062835e669dc",
             "size": 13759084,