lint: make output of apkbuild-lint easy to spot

The output of apkbuild-lint is hard to spot among other log messages
from pmbootstrap, because it is not colorized.

Add "*** " before and after the output of apkbuild-lint, so we get three
dots in green color before and after. The space is needed, or else it
will not be colored. (We could change that too, but the extra space
prevents it from coloring text unintendedly.)

pmb/helpers/lint.py

@@ -57,6 +57,9 @@ def check(pkgnames: Sequence[str]):
     logging.info(f"(native) linting {pkgstr} with apkbuild-lint")
     options = pmb.config.apkbuild_custom_valid_options
 
+    # apkbuild-lint output is not colorized, make it easier to spot
+    logging.info("*** apkbuild-lint output ***")
+
     # For each pkgrepo run the linter on the relevant packages
     has_failed = False
     for pkgrepo, apkbuild_paths in apkbuilds.items():
@@ -69,5 +72,7 @@ def check(pkgnames: Sequence[str]):
         ):
             has_failed = True
 
+    logging.info("*** apkbuild-lint output ***")
+
     if has_failed:
         raise NonBugError("Linter failed!")