Packages (Linux): add Linglong support (#1214)

Support for counting Linglong applications installed in Deepin, Ubuntu and Debian distros.

Packages are installed using the ``ll-cli`` package manager frontend:
https://linglong.dev/guide/ll-cli/introduction.html#ll-cli%E7%AE%80%E4%BB%8B

---------

Co-authored-by: Carter Li <CarterLi@users.noreply.github.com>

src/detection/packages/packages.h

@@ -17,6 +17,7 @@ typedef struct FFPackagesResult
     uint32_t guixHome;
     uint32_t guixSystem;
     uint32_t guixUser;
+    uint32_t linglong;
     uint32_t lpkg;
     uint32_t lpkgbuild;
     uint32_t nixDefault;

src/detection/packages/packages_linux.c

@@ -471,6 +471,7 @@ static void getPackageCounts(FFstrbuf* baseDir, FFPackagesResult* packageCounts,
     {
       packageCounts->guixSystem += getGuixPackages(baseDir, "/run/current-system/profile");
     }
+    if (!(options->disabled & FF_PACKAGES_FLAG_LINGLONG_BIT)) packageCounts->linglong += getNumElements(baseDir, "/var/lib/linglong/repo/refs/heads/main", DT_DIR);
 }
 
 static void getPackageCountsRegular(FFstrbuf* baseDir, FFPackagesResult* packageCounts, FFPackagesOptions* options)