Bug#907570: libmodule-install-perl: install_script shouldn't change the shebang to realpath

[Shengjing Zhu]

Package: libmodule-install-perl
Severity: important
Control: affects -1 dh-golang

Dear Maintainer,

Disclaim: I'm poor at perl.

When build dh-golang in a usrmerged chroot, the shebang of the bash script[1]
installed[2] by `install_script` is changed to /usr/bin/bash.

I think the `install_script` command is provided by
libmodule-install-perl.

It happens when I build dh-golang with sbuild.

By default, sbuild-createchroot calls debootstrap to create the chroot.
And the default behaviour of debootstrap is to create a chroot that
makes /{bin,sbin,lib}/ symlinks to /usr/. So in the chroot, /bin/bash
symlinks to /usr/bin/bash.

I'm not sure if the usrmerge is enabled by default in Debian or not.
But I find many Debian systems is not usrmerged.

As a result, the bash script installed by libmodule-install-perl failed
to run on my system.

I don't known why libmodule-install-perl wants to manipulate the shebang
when the origin shebang exists.

P.S. It seems the chroot on buildd is not usrmerged, so the dh-golang
package in the archive has the correct shebang.

[1] https://sources.debian.org/src/dh-golang/1.35/script/dh_golang_autopkgtest/
[2] https://sources.debian.org/src/dh-golang/1.35/Makefile.PL/#L7

-- 
Shengjing Zhu