Fix shell_check()

Change the shell_check to check the current shell, instead of the default shell

misc/build.func

@@ -73,7 +73,7 @@ msg_error() {
 
 # Check if the shell is using bash
 shell_check() {
-  if [[ "$(basename "$SHELL")" != "bash" ]]; then
+  if [[ "$(basename "$0")" != "bash" ]]; then
     clear
     msg_error "Your default shell is currently not set to Bash. To use these scripts, please switch to the Bash shell."
     echo -e "\nExiting..."