Add blinky post-synthesis testbench

Signed-off-by: Clifford Wolf <clifford@clifford.at>

ice40/.gitignore

@@ -1,5 +1,4 @@
-/chipdb-1k.cc
-/chipdb-384.cc
-/chipdb-5k.cc
-/chipdb-8k.cc
-chipdbs/
+/blinky_chip.v
+/blinky_tb
+/blinky_tb.vcd
+/chipdbs/

ice40/blinky.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+set -ex
+yosys blinky.ys
+../nextpnr-ice40 --json blinky.json --asc blinky.asc
+icebox_vlog blinky.asc > blinky_chip.v
+iverilog -o blinky_tb blinky_chip.v blinky_tb.v
+./blinky_tb

ice40/blinky_tb.v

@@ -0,0 +1,15 @@
+module blinky_tb;
+    reg clk;
+    always #5 clk = (clk === 1'b0);
+
+    chip uut (
+        .io_0_8_1(clk)
+    );
+
+    initial begin
+        $dumpfile("blinky_tb.vcd");
+        $dumpvars(0, blinky_tb);
+        repeat (9000000) @(posedge clk);
+        $finish;
+    end
+endmodule