Restore fallback installs for audio and vision; move print statement; update docs url

Author: keyprocedure

install_requirements.py

@@ -79,6 +79,11 @@ def install_requirements(use_pytorch_nightly):
 
     # Skip pip install on Intel macOS if using nightly.
     if use_pytorch_nightly and is_intel_mac:
+        print(
+            "ERROR: Prebuilt PyTorch wheels are no longer available for Intel-based macOS.\n"
+            "Please build from source by following https://docs.pytorch.org/executorch/main/using-executorch-building-from-source.html",
+            file=sys.stderr,
+        )
         sys.exit(1)
 
     # pip packages needed by exir.
@@ -92,14 +97,20 @@ def install_requirements(use_pytorch_nightly):
     EXAMPLES_REQUIREMENTS = []
 
     # Only pip install torchvision and torchaudio if not building PyTorch from source on Intel macOS,
-    # to avoid installing incompatible prebuilt wheels from PyPI.
+    # to avoid having incompatible prebuilt wheels from PyPI installed.
     if not is_intel_mac:
         EXIR_REQUIREMENTS.append(
             f"torchvision==0.22.0.{NIGHTLY_VERSION}"
+            if use_pytorch_nightly
+            else "torchvision"
         )  # For testing.
 
         EXAMPLES_REQUIREMENTS = [
-            f"torchaudio==2.6.0.{NIGHTLY_VERSION}",
+            (
+                f"torchaudio==2.6.0.{NIGHTLY_VERSION}"
+                if use_pytorch_nightly
+                else "torchaudio"
+            )
         ]
 
     # Assemble the list of requirements to actually install.
@@ -156,18 +167,11 @@ def install_requirements(use_pytorch_nightly):
 # 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 macOS
-    if platform.system().lower() == "darwin" and platform.machine().lower() in (
+    return platform.system().lower() == "darwin" and platform.machine().lower() in (
         "x86",
         "x86_64",
         "i386",
-    ):
-        print(
-            "ERROR: Prebuilt PyTorch wheels are no longer available for Intel-based macOS.\n"
-            "Please build 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):