Add intel-macOS system check

Author: keyprocedure

install_requirements.py

@@ -75,6 +75,10 @@ def python_is_compatible():
 
 
 def install_requirements(use_pytorch_nightly):
+    # Prevent pip install attempt on Intel-based macOS (no prebuilt PyTorch binaries available)
+    if use_pytorch_nightly and is_intel_mac_os():
+        sys.exit(1)
+
     # pip packages needed by exir.
     EXIR_REQUIREMENTS = [
         # Setting use_pytorch_nightly to false to test the pinned PyTorch commit. Note
@@ -139,6 +143,24 @@ def install_requirements(use_pytorch_nightly):
     )
 
 
+# Prebuilt binaries for Intel-based macOS are no longer available on PyPI; users must compile from source.
+# PyTorch stopped building macOS x86_64 binaries since version 2.3.0 (January 2024).
+def is_intel_mac_os():
+    # Returns True if running on Intel-based macOS
+    if platform.system().lower() == "darwin" and platform.machine().lower() in (
+        "x86",
+        "x86_64",
+        "i386",
+    ):
+        print(
+            "ERROR: Prebuilt PyTorch binaries are no longer available for Intel-based macOS.\n"
+            "Please compile from source by following https://pytorch.org/executorch/0.6/using-executorch-building-from-source.html",
+            file=sys.stderr,
+        )
+        return True
+    return False
+
+
 def main(args):
     parser = argparse.ArgumentParser()
     parser.add_argument(