bug#74450: patch-shebang does not work with '/usr/bin/env -S'

[Théo Tyburn]

Hi guix,

I noticed that 'patch-shebang' in (guix build utils) does not work if
the shebang is something like '#!/usr/bin/env -S python3 -u'. So it is
not able to patch shebangs with multiple arguments
https://www.gnu.org/software/coreutils/manual/html_node/env-invocation.html#g_t_002dS_002f_002d_002dsplit_002dstring-usage-in-scripts

With the shebang above I get this error in the build phase:
"patch-shebang: main.py: warning: no binary for interpreter `-S' found
in $PATH". By looking at the function, this makes sense since in the
let* bindings 'cmd' is bind to 'arg1' which is just '-S'. So the fix
would not be too hard to implement.

Cheers,

Théo