Prefer system check which result in a new recipe should be treated as normal packages

In general when are remote store is provided, we disable system packages. However, this
should not be the case if the system package results in a new recipe, because in that case
we consider the result of that recipe to be the package.

Author: ktf

alibuild_helpers/utilities.py

@@ -504,8 +504,8 @@ def getPackageList(packages, specs, configDir, preferSystem, noSystem,
       noSystemList = [spec["package"]]
     elif noSystem is not None:
       noSystemList = noSystem.split(",")
-
-    if (spec["package"] not in noSystemList) and (preferSystem or systemREMatches):
+    systemExcluded = (spec["package"] in noSystemList)
+    if (preferSystem or systemREMatches):
       requested_version = resolve_version(spec, defaults, "unavailable", "unavailable")
       cmd = "REQUESTED_VERSION={version}\n{check}".format(
         version=quote(requested_version),
@@ -520,12 +520,16 @@ def getPackageList(packages, specs, configDir, preferSystem, noSystem,
       else:
         # prefer_system_check succeeded; this means we should use the system package.
         match = re.search(r"^alibuild_system_replace:(?P<key>.*)$", output, re.MULTILINE)
-        if not match:
+        if not match and systemExcluded:
+          # No replacement spec name given. Fall back to old system package
+          # behaviour and just disable the package.
+          ownPackages.add(spec["package"])
+        elif not match and not systemExcluded:
           # No replacement spec name given. Fall back to old system package
           # behaviour and just disable the package.
           systemPackages.add(spec["package"])
           disable.append(spec["package"])
-        else:
+        elif match:
           # The check printed the name of a replacement; use it.
           key = match.group("key").strip()
           replacement = None