src/winusb: Defensive Bash Programming: readonly all function definit…

…ions

Signed-off-by: 林博仁 <[email protected]>

src/winusb

@@ -677,7 +677,7 @@ echo_with_color(){
 		echo -e "${message_body}"
 		switch_terminal_text_color none
 	fi
-}
+}; declare -fr echo_with_color
 
 # Unmount mounted filesystems and clean-up mountpoints before exiting program
 # $1: Windows ISO mountpoint
@@ -729,7 +729,7 @@ cleanup_mountpoints(){
 	else
 		exit 2
 	fi
-}
+}; declare -fr cleanup_mountpoints
 
 hideNoErr(){
 	set +o errexit
@@ -753,7 +753,7 @@ hideNoErr(){
 	fi
 
 	return "$RETURN"
-}
+}; declare -fr hideNoErr
 
 # Copy source_file to dest_file, overwrite file if dest_file exists
 # Also report copy_filesystem_files progress during operation
@@ -872,7 +872,7 @@ copy_filesystem_files(){
 	pulse on
 
 	return 0
-}
+}; declare -fr copy_filesystem_files
 
 print_help(){
 	util_check_function_parameters_quantity 0 "${#}"