win32: dirs-uap: handle VLC_PKG_LIB_DIR/VLC_PKG_LIBEXEC_DIR

This is the same implementation as in desktop Windows.

GetModuleFileNameW [^1] and VirtualQuery [^2] are available in UWP.

[^1]: https://learn.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-getmodulefilenamew#requirements
[^2]: https://learn.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-virtualquery#requirements

src/win32/dirs-uap.c

@@ -153,10 +153,47 @@ end_other:
     return GetFolderName(folder);
 }
 
+char *config_GetLibDir (void)
+{
+    /* Get our full path */
+    MEMORY_BASIC_INFORMATION mbi;
+    if (!VirtualQuery (config_GetLibDir, &mbi, sizeof(mbi)))
+        goto error;
+
+    wchar_t wpath[MAX_PATH];
+    if (!GetModuleFileNameW ((HMODULE) mbi.AllocationBase, wpath, MAX_PATH))
+        goto error;
+
+    wchar_t *file = wcsrchr (wpath, L'\\');
+    if (file == NULL)
+        goto error;
+    *file = L'\0';
+
+    return FromWide (wpath);
+error:
+    abort ();
+}
+
+static char *config_GetLibexecDir (void)
+{
+    wchar_t wpath[MAX_PATH];
+    if (!GetModuleFileNameW (NULL, wpath, MAX_PATH))
+        goto error;
+
+    wchar_t *file = wcsrchr (wpath, L'\\');
+    if (file == NULL)
+        goto error;
+    *file = L'\0';
+
+    return FromWide (wpath);
+error:
+    abort ();
+}
+
 static char *config_GetDataDir(void)
 {
     const char *path = getenv ("VLC_DATA_PATH");
-    return (path != NULL) ? strdup (path) : NULL;
+    return (path != NULL) ? strdup (path) : config_GetLibDir ();
 }
 
 char *config_GetSysPath(vlc_sysdir_t type, const char *filename)
@@ -172,8 +209,11 @@ char *config_GetSysPath(vlc_sysdir_t type, const char *filename)
             dir = getenv ("VLC_LIB_PATH");
             if (dir)
                 return strdup( dir );
-            /* fallthrough */
+            dir = config_GetLibDir();
+            break;
         case VLC_PKG_LIBEXEC_DIR:
+            dir = config_GetLibexecDir();
+            break;
         case VLC_SYSDATA_DIR:
             return NULL;
         case VLC_LOCALE_DIR: