pmbootstrap downgrades packages built with --src

@drebrez discovered the following bug (more detailed report in #1672 (comment 116148860)).

This works as expected:

$ pmbootstrap build linux-samsung-klte
(creates ~/.local/var/pmbootstrap/packages/armhf/linux-samsung-klte-3.4.113-r0.apk)
$ pmbootstrap build --src=/path/to/sources linux-samsung-klte
(creates ~/.local/var/pmbootstrap/packages/armhf/linux-samsung-klte-3.4.113_p20181110001756-r0.apk)
$ pmbootstrap zap
$ pmbootstrap chroot -r -- apk add linux-samsung-klte
(installs latest version)
$ pmbootstrap flasher flash_kernel
(installs remaining packages, creates initfs and flashes it)

Now things go south (commands ran after the ones above):

$ pmbootstrap build --src=/path/to/sources linux-samsung-klte
(creates ~/.local/var/pmbootstrap/packages/armhf/linux-samsung-klte-3.4.113_p20181110013854-r0.apk, higher number!)
$ pmbootstrap flasher flash_kernel
(020114) [00:49:23] (rootfs_samsung-klte) calculate depends of device-samsung-klte, device-samsung-klte-kernel-downstream (pmbootstrap -v for details)
(020114) [00:49:25] WARNING: Package 'linux-samsung-klte' in your aports folder has version 3.4.113-r0, but the binary package repositories already already have version 3.4.113_p20181110013854-r0! See also: <https://postmarketos.org/warning-repo2>
(020114) [00:49:25] (rootfs_samsung-klte) install
(020114) [00:49:25] (rootfs_samsung-klte) % apk --no-progress add -u --virtual .pmbootstrap /mnt/pmbootstrap-packages/armhf/linux-samsung-klte-3.4.113-r0.apk
(1/2) Downgrading linux-samsung-klte (3.4.113_p20181110001756-r0 -> 3.4.113-r0)
(2/2) Installing .pmbootstrap (0)
...

@drebrez wrote this patch to fix it:

--- a/pmb/chroot/apk.py
+++ b/pmb/chroot/apk.py
@@ -168,10 +168,9 @@ def replace_aports_packages_with_path(args, packages, suffix, arch):
     for package in packages:
         aport = pmb.build.find_aport(args, package, False)
         if aport:
-            apkbuild = pmb.parse.apkbuild(args, aport + "/APKBUILD")
+            data_repo = pmb.parse.apkindex.package(args, package, arch, False)
             apk_path = ("/mnt/pmbootstrap-packages/" + arch + "/" +
-                        package + "-" + apkbuild["pkgver"] + "-r" +
-                        apkbuild["pkgrel"] + ".apk")
+                        package + "-" + data_repo["version"] + ".apk")
             if os.path.exists(args.work + "/chroot_" + suffix + apk_path):
                 package = apk_path
         ret.append(package)