util: use env to call bash in shell scripts

- For shell scripts using bash, use #!/usr/bin/env bash instead of #!/bin/bash.
    On some OS, bash is not the default shell and is not installed as /bin/bash

Signed-off-by: Laurent Cheylus <foxy@free.fr>

util/build-gnu.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # `build-gnu.bash` ~ builds GNU coreutils (from supplied sources)
 #