Add alpine to libbpf availability

[patricoferris]

A bit like #27903 but for alpine.

[mseri]

The whitespace change looks inconsistent with the rest of the file imo.

Unfortunately this is still not working:

libbpf.0.1.0 is not installed. Install it? [y/n] y
  * Missing dependency:
    - libbpf -> conf-clang
    depends on the unavailable system package 'clang'. Use `--no-depexts' to attempt installation anyway, or it is possible that a depext package name in the opam file is incorrect.

[patricoferris]

The whitespace change looks inconsistent with the rest of the file imo.

Indeed, the files were all over the place with tabs and spaces. I have updated them to be consistent. I had a look for some opam files formatting tool and couldn't easily find one, did I miss it? It would be nice to not be blocked on that kind of thing I think.

I also added alpine and nixos availability to bpftool too. Waiting to see what CI makes of it.

Thank you for the reviews :)

[mseri]

We should re-run the tests once #28290 is merged

[mseri]

Now that alpine works, this is still failing with

#=== ERROR while compiling libbpf.0.1.0 =======================================#
# context              2.3.0 | linux/x86_64 | ocaml-base-compiler.4.14.2 | pinned(https://github.com/koonwen/ocaml-libbpf/releases/download/v0.1.0/libbpf-0.1.0.tbz)
# path                 ~/.opam/4.14/.opam-switch/build/libbpf.0.1.0
# command              ~/.opam/opam-init/hooks/sandbox.sh build dune build -p libbpf -j 255 @install
# exit-code            1
# env-file             ~/.opam/log/libbpf-7-e0d484.env
# output-file          ~/.opam/log/libbpf-7-e0d484.out
### output ###
# File "src/bindings/stubgen/dune", lines 13-18, characters 0-197:
# 13 | (rule
# 14 |  (targets gen_type_bindings_from_c.exe)
# 15 |  (deps gen_type_bindings.c)
# 16 |  (action
# 17 |   (bash
# 18 |    "%{cc} %{deps} -I `dirname %{lib:ctypes:ctypes_cstubs_internals.h}` -I %{ocaml_where} -o %{targets}")))
# (cd _build/default/src/bindings/stubgen && /bin/bash -e -u -o pipefail -c 'gcc -O2 -fno-strict-aliasing -fwrapv -pthread -fPIC -D_FILE_OFFSET_BITS=64 -Wall -fdiagnostics-color=always gen_type_bindings.c -I `dirname /home/opam/.opam/4.14/lib/ctypes/ctypes_cstubs_internals.h` -I /home/opam/.opam/4.14/lib/ocaml -o gen_type_bindings_from_c.exe')
# gen_type_bindings.c:1:10: fatal error: bpf/libbpf.h: No such file or directory
#     1 | #include <bpf/libbpf.h>
#       |          ^~~~~~~~~~~~~~
# compilation terminated.

[mseri]

I think the package may need some further updates to work with alpine