otp_build: Refuse if current directory is not under ERL_TOP

Author: sverker

otp_build

@@ -137,6 +137,15 @@ check_erltop ()
 		    echo "The environment variable ERL_TOP must be set." >&2
 		    exit 1
 		fi
+	else
+	    real_ERL_TOP=`realpath $ERL_TOP`
+	    real_PWD=`realpath $PWD`
+	    if [ "X${real_PWD##$real_ERL_TOP*}" != "X" ]; then
+		echo "Current working directory is not in ERL_TOP." >&2
+		echo "ERL_TOP=$ERL_TOP" >&2
+		echo "PWD=$PWD" >&2
+		exit 1
+	    fi
 	fi
 }