aportgen musl-*: use 'busybox tar' in package() too

Follow up to last commit, turns out we need to use it in both functions
or otherwise at least gitlab-ci can fail, as seen in this MR:
https://gitlab.com/postmarketOS/pmaports/merge_requests/270

After using 'busybox tar' instead of 'tar' in both places in the
APKBUILDs, it went through.

pmb/aportgen/musl.py

@@ -95,7 +95,9 @@ def generate(args, pkgname):
             package() {
                 mkdir -p "$pkgdir/usr/$_target"
                 cd "$pkgdir/usr/$_target"
-                tar -xf $srcdir/musl-$pkgver-r$pkgrel-$_arch.apk
+                # Use 'busybox tar' to avoid 'tar: Child returned status 141'
+                # on some machines (builds.sr.ht, gitlab-ci). See pmaports#26.
+                busybox tar -xf $srcdir/musl-$pkgver-r$pkgrel-$_arch.apk
                 rm .PKGINFO .SIGN.*
             }
             package_dev() {