tests: use /usr/bin/env for bash.

techlibs/ice40/tests/test_bram.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 
 set -ex
 

techlibs/ice40/tests/test_dsp_map.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -ex
 
 for iter in {1..100}

techlibs/ice40/tests/test_dsp_model.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -ex
 sed 's/SB_MAC16/SB_MAC16_UUT/; /SB_MAC16_UUT/,/endmodule/ p; d;' < ../cells_sim.v > test_dsp_model_uut.v
 if [ ! -f "test_dsp_model_ref.v" ]; then

techlibs/ice40/tests/test_ffs.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -ex
 for CLKPOL in 0 1; do
 for ENABLE_EN in 0 1; do