feat: make INSTALL_PATH overridable in install script (#3954)

Allow users to override the installation path by setting the INSTALL_PATH
environment variable before running the script.

This can be useful in CI environments such as CircleCI where the default
/usr/local/bin path requires sudo privileges that may not be available or desired.

Usage:
- Default: curl -sSL https://get.livekit.io/cli | bash
- Custom: INSTALL_PATH="$HOME/.local/bin" curl -sSL https://get.livekit.io/cli | bash

install-livekit.sh

@@ -21,7 +21,7 @@ set -o errexit
 set -o pipefail
 
 REPO="livekit"
-INSTALL_PATH="/usr/local/bin"
+INSTALL_PATH="${INSTALL_PATH:-/usr/local/bin}"
 
 log()  { printf "%b\n" "$*"; }
 abort() {