board/common: let Bash update its PS1 hostname for each new line

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/rootfs/etc/bash.bashrc

@@ -3,6 +3,13 @@
 # If not running interactively, don't do anything
 [ -z "$PS1" ] && return
 
+# Reevaluate for each line, in case hostname changes
+function prompt_command
+{
+    PS1="\u@$(hostname):\w\$ "
+}
+export PROMPT_COMMAND=prompt_command
+
 # check the window size after each command and, if necessary,
 # update the values of LINES and COLUMNS.
 shopt -s checkwinsize