NuttX-Posix least bad LGD

Nuttx now supports sh and source (.)
   sh will open a new process for each invocation.
   This means the child can not modify the parent
   env. So we must use . to matain how nuttx worked.

   Since rc.vehicle_setup is used in both we use
   source and alis as we did with sh.

platforms/posix/src/px4/common/px4-alias.sh_in

@@ -28,6 +28,19 @@ sh() {
 	. "$(pwd)$script"
 }
 
+source() {
+	script="$1"
+	case "$script" in
+	"/"*)
+		script="$script"
+		;;
+	*)
+		script="/$script"
+		;;
+	esac
+	. "$(pwd)$script"
+}
+
 # Don't stop on errors.
 #set -e