Fix build script issues on non apple platforms

Author: dgovil

README.md

@@ -202,6 +202,8 @@ This command takes an optional list of targets to build, but will otherwise buil
 > python OpenUSD/build_scripts/apple_utils.py xcframework /path/to/my_usd_install_dir
 ```
 
+Note that currently, Simulator builds do not render with Imaging as Simulator targets have reduced Metal support.
+
 ##### Windows:
 
 Launch the "x64 Native Tools Command Prompt" for your version of Visual Studio

build_scripts/build_usd.py

@@ -2785,7 +2785,7 @@ def FormatBuildArguments(buildArgs):
     Print("See documentation at http://openusd.org/docs/RenderMan-USD-Imaging-Plugin.html "
           "for setting up the RenderMan plugin.\n")
 
-if context.buildAppleFramework:
+if MacOS() and context.buildAppleFramework:
     Print("""
         Add the following framework to your Xcode Project:
         OpenUSD.framework