fix: alert users that darwin is not supported (pytorch#15289)

### Summary

Add a note for the users that try to follow the tutorials on
Apple/Darwin systems

Author: Mistobaan

backends/qualcomm/scripts/build.sh

@@ -5,14 +5,22 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 set -e
-set -o xtrace
+
+# Check if running on macOS/Darwin
+if [[ "$(uname -s)" == "Darwin" ]]; then
+    echo "Error: Qualcomm backend Python interface requires Linux operating system."
+    echo "macOS/Darwin is not supported for building the Qualcomm backend."
+    echo "Please use a x64 Linux system or x64 Linux container to build this backend."
+    exit 1
+fi
 
 if [[ -z ${QNN_SDK_ROOT} ]]; then
     echo "Please export QNN_SDK_ROOT=/path/to/qnn_sdk"
     exit -1
 fi
 
 
+set -o xtrace
 
 usage() {
   echo "Usage: Build the aarch64 version of executor runner or the python interface of Qnn Manager"