pw_env_setup: Use ${platform} path in compat CIPD

Use '${platform}' instead of more specific paths in the
compatibility.json CIPD file.

Bug: b/246971220
Change-Id: I58f9448eaa8669c338ee198c730ac6c4e23f629c
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/110531
Pigweed-Auto-Submit: Rob Mohr <mohrr@google.com>
Reviewed-by: Ted Pudlik <tpudlik@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_env_setup/py/pw_env_setup/cipd_setup/compatibility.json b/pw_env_setup/py/pw_env_setup/cipd_setup/compatibility.json
index 6d771ef..97150cf 100644
--- a/pw_env_setup/py/pw_env_setup/cipd_setup/compatibility.json
+++ b/pw_env_setup/py/pw_env_setup/cipd_setup/compatibility.json
@@ -1,7 +1,7 @@
 {
   "packages": [
     {
-      "path": "infra/3pp/tools/cpython3/${os}-${arch=amd64}",
+      "path": "infra/3pp/tools/cpython3/${platform}",
       "platforms": [
         "linux-amd64",
         "linux-arm64",
@@ -14,7 +14,7 @@
       ]
     },
     {
-      "path": "pigweed/third_party/gcc-arm-none-eabi/${os}-${arch=amd64}",
+      "path": "pigweed/third_party/gcc-arm-none-eabi/${platform}",
       "platforms": [
         "linux-amd64",
         "mac-amd64",