Preserve AppImage files; do not extract them

My previous fixes here were misguided. Those AppImage files must not be
extracted at all or they won't work.

I've created a sort of dumb extractor function for them that just copies
the .AppImage file; this avoids letting 7-zip ever see them, so they don't
get damaged.

lutris/util/extract.py

@@ -87,6 +87,8 @@ def guess_extractor(path):
         extractor = "exe"
     elif path.endswith(".deb"):
         extractor = "deb"
+    elif path.endswith(".AppImage"):
+        extractor = "AppImage"
     else:
         extractor = None
     return extractor
@@ -113,6 +115,8 @@ def get_archive_opener(extractor):
         opener = "exe"
     elif extractor == "deb":
         opener = "deb"
+    elif extractor == "AppImage":
+        opener = "AppImage"
     else:
         opener = "7zip"
     return opener, mode
@@ -187,6 +191,8 @@ def _do_extract(archive, dest, opener, mode=None, extractor=None):
         extract_gog(archive, dest)
     elif opener == "deb":
         extract_deb(archive, dest)
+    elif opener == "AppImage":
+        extract_AppImage(archive, dest)
     else:
         handler = opener(archive, mode)
         handler.extractall(dest)
@@ -233,6 +239,13 @@ def extract_deb(archive, dest):
             break
 
 
+def extract_AppImage(path, dest):
+    """This is really here to prevent 7-zip from extracting the AppImage;
+    we want to just use this sort of file as-is."""
+    system.create_folder(dest)
+    shutil.copy(path, dest)
+
+
 def extract_gog(path, dest):
     if check_inno_exe(path):
         decompress_gog(path, dest)

share/lutris/json/basiliskii.json

@@ -3,7 +3,7 @@
     "description": "Basilisk II is an Open Source 68k Macintosh emulator",
     "platforms": ["Macintosh"],
     "runnable_alone": "True",
-    "runner_executable": "basiliskii/usr/bin/BasiliskII",
+    "runner_executable": "basiliskii/BasiliskII-x86_64.AppImage",
     "download_url": "https://github.com/Korkman/macemu-appimage-builder/releases/download/continuous/BasiliskII-x86_64.AppImage",
     "game_options": [
         {

share/lutris/json/sheepshaver.json

@@ -3,7 +3,7 @@
     "description": "SheepShaver emulates a PowerMacintosh computer",
     "platforms": ["Macintosh"],
     "runnable_alone": "True",
-    "runner_executable": "sheepshaver/usr/bin/SheepShaver",
+    "runner_executable": "sheepshaver/SheepShaver-x86_64.AppImage",
     "download_url": "https://github.com/Korkman/macemu-appimage-builder/releases/download/continuous/SheepShaver-x86_64.AppImage",
     "game_options": [
         {