Update on "Install libcpp from release package other than apt-get"

A few changes

1. Use the release package from https://releases.llvm.org/ to install libcpp, so we can install from different linux in addition to Ubuntu
2. Seperate out the qnn version and the url to a seperate file, for better versin management in the future

Differential Revision: [D77048745](https://our.internmc.facebook.com/intern/diff/D77048745/)

Differential Revision: [D77048745](https://our.internmc.facebook.com/intern/diff/D77048745)

[ghstack-poisoned]

Author: cccclai

backends/qualcomm/scripts/install_qnn_sdk.sh

@@ -7,8 +7,11 @@
 
 set -ex
 
-# Source QNN configuration
-source "$(dirname "$0")/qnn_config.sh"
+# Get the absolute path of this script
+SCRIPT_DIR="$( cd -- "$(dirname "${BASH_SOURCE[0]}")" >/dev/null 2>&1 ; pwd -P )"
+
+# Source QNN configuration from the same directory
+source "${SCRIPT_DIR}/qnn_config.sh"
 
 # Function to install Android NDK (only if not already set)
 setup_android_ndk() {