[DO NOT MERGE] Temporarily force PR builds to test 3.15/3.15t on Linux

PR builds normally limit to python_versions[0] (3.10); override that to
["3.15", "3.15t"] for linux and linux-aarch64 so this PR's CI actually
exercises the new versions (macOS/Windows keep 3.10 to avoid an empty
matrix). Revert this commit before merging.

Authored with assistance from Claude Code (AI assistant).

Author: atalman

tools/scripts/generate_binary_build_matrix.py

@@ -448,6 +448,8 @@ def generate_wheels_matrix(
 ) -> List[Dict[str, str]]:
     package_type = "wheel"
 
+    explicitly_requested_versions = bool(python_versions)
+
     if not python_versions:
         # Define default python version
         python_versions = list(PYTHON_ARCHES)
@@ -488,7 +490,15 @@ def generate_wheels_matrix(
             arches += [XPU]
 
     if limit_pr_builds:
-        python_versions = [python_versions[0]]
+        # TEMPORARY (DO NOT MERGE): force the default PR build selection to
+        # exercise 3.15 / 3.15t on Linux so this PR's CI validates the new
+        # versions. Callers that pass an explicit python-versions list (e.g. the
+        # ExecuTorch self-test, which pins 3.10/3.11 because it caps <3.15) keep
+        # theirs. Revert to `python_versions = [python_versions[0]]` before merging.
+        if not explicitly_requested_versions and os in (LINUX, LINUX_AARCH64):
+            python_versions = ["3.15", "3.15t"]
+        else:
+            python_versions = [python_versions[0]]
 
     global WHEEL_CONTAINER_IMAGES