install-vmod shebang does not work on linux/arm64 architecture

[thomasklinger1234]

Observed Behavior

When I run install-vmod -h in a Docker container (e.g. varnish:7.5.0) with --platform=linux/arm64 or similar it breaks with the following exception:

#10 [builder  4/13] RUN set -ex;     /usr/local/bin/install-vmod -h
#10 0.087 + /usr/local/bin/install-vmod -h
#10 0.096 Error while loading /usr/local/bin/install-vmod: Exec format error
#10 ERROR: process "/dev/.buildkit_qemu_emulator /bin/sh -c set -ex;     /usr/local/bin/install-vmod -h" did not complete successfully: exit code: 1
------
 > [builder  4/13] RUN set -ex;     /usr/local/bin/install-vmod -h:
/usr/local/bin/install-vmod -h
0.096 Error while loading /usr/local/bin/install-vmod: Exec format error
------
Dockerfile:31
--------------------
  30 |     
  31 | >>> RUN set -ex; \
  32 | >>>     /usr/local/bin/install-vmod -h
  33 |     
--------------------

Expected Behavior

I tracked it down to the shebang in https://github.com/varnish/toolbox/blob/master/install-vmod/install-vmod#L1 not being recognized somehow on ARM based docker images or runtimes.

Possible Solution

After changing the shebang to either #!/bin/sh or #!/usr/bin/env bash the script magically worked. To keep compatbility with the existing script and also keep minimal distros like Alpine in mind, the fixt might be:

- #/bin/sh
+ #!/bin/sh

Background

Wikipedia also mentiones the special syntax for shebangs as #! so the current implementation might only work due to luck or amd variants having special fallbacks or syntax for first-line during execution.