pmbootstrap dependency resolving fails on fuzzy versions

Created by: ollieparanoid

@michitux reported in #postmarketOS:

Then I tried packaging it for Alpine but I failed to package ocaml-num (+ I am not sure if there is a packaging problem in Alpine or if the pmOS dependency parser has a bug - according to the pmOS parser, ocaml-camlp4 has an unsatisfiable dependency, but in the chroot I can install it without any problems).

From the log:

...
(011656) [14:05:46] ocaml-camlp4: depends on: ocaml-runtime~4.06,ocaml-ocamlbuild
...
(011656) [14:05:46] ERROR: Could not find package 'ocaml-runtime~4.06' in any aports folder or APKINDEX.
(011656) [14:05:46] Run 'pmbootstrap log' for details.
(011656) [14:05:46] See also: <https://postmarketos.org/troubleshooting>
(011656) [14:05:46] Traceback (most recent call last):
  File "/home/michitux/Code/pmbootstrap/pmb/__init__.py", line 61, in main
    getattr(frontend, args.action)(args)
  File "/home/michitux/Code/pmbootstrap/pmb/helpers/frontend.py", line 133, in build
    args.strict, src=src):
  File "/home/michitux/Code/pmbootstrap/pmb/build/_package.py", line 424, in package
    skip_init_buildenv, src):
  File "/home/michitux/Code/pmbootstrap/pmb/build/_package.py", line 185, in init_buildenv
    pmb.chroot.apk.install(args, depends, suffix)
  File "/home/michitux/Code/pmbootstrap/pmb/chroot/apk.py", line 195, in install
    packages_with_depends = pmb.parse.depends.recurse(args, packages, suffix)
  File "/home/michitux/Code/pmbootstrap/pmb/parse/depends.py", line 159, in recurse
    "' in any aports folder or APKINDEX.")
RuntimeError: Could not find package 'ocaml-runtime~4.06' in any aports folder or APKINDEX.