fix: keep a buildbot core beside its standalone

installable_cores removed every buildbot name the image builds, so a
libretro core sharing its name with a standalone package was lost:
Batocera runs amiberry standalone and its x86_64 boards fetch
amiberry_libretro. A name now compares within its build mode, and the
resolver and the layouts treat such a core as the emulator's libretro
build, run both ways. Batocera gains amiberry, azahar, cannonball, cemu,
dosbox, ecwolf, eduke32, fsuae, openmsx, rpcs3, supermodel, vita3k, xemu
and ymir as installable, KNULLI cannonball.

scripts/common.py

@@ -2767,6 +2767,15 @@ def standalone_set(config: dict) -> set[str]:
     """
     names = {str(c) for c in config.get("standalone_cores") or []}
     names |= {DUAL_MODE_PREFIX + str(c) for c in config.get("dual_mode_cores") or []}
+    # A buildbot core the platform's RetroArch installs under the name of an
+    # emulator it runs standalone is that emulator's libretro build: run
+    # both ways, as Batocera runs amiberry standalone and can fetch
+    # amiberry_libretro.
+    names |= {
+        DUAL_MODE_PREFIX + str(c)
+        for c in set(map(str, config.get("installable_cores") or []))
+        & set(map(str, config.get("standalone_cores") or []))
+    }
     # The system directory each core is handed travels the same way, so
     # platform_layouts places a core's files below it for every reader.
     names |= {
@@ -3264,10 +3273,13 @@ def resolve_platform_cores(
         # A name the platform launches both ways designates its libretro
         # build too. Batocera, Recalbox and RetroBat run pcsx2 standalone and
         # as LRPS2, two profiles: the key match kept the standalone one and
-        # LRPS2's files never reached their packs.
+        # LRPS2's files never reached their packs. A core its RetroArch
+        # installs is a libretro build as well (amiberry's buildbot core
+        # beside Batocera's standalone amiberry).
         result |= {
             profile
-            for c in config.get("dual_mode_cores") or []
+            for c in [*(config.get("dual_mode_cores") or []),
+                      *(config.get("installable_cores") or [])]
             for profile in index.get(str(c), set())
             if "libretro" in str(profiles[profile].get("type", ""))
             and not profiles[profile].get("built_by")