Add cli option to set the verbosity level

The verbosity was set either to info (in release mode) or debug (in
debug mode).

Add a command-line argument to change it, so that users can enable debug
logs using the release:

    scrcpy -Vdebug

app/src/main.c

@@ -29,6 +29,24 @@ print_version(void) {
                                                LIBAVUTIL_VERSION_MICRO);
 }
 
+static SDL_LogPriority
+convert_log_level_to_sdl(enum sc_log_level level) {
+    switch (level) {
+        case SC_LOG_LEVEL_DEBUG:
+            return SDL_LOG_PRIORITY_DEBUG;
+        case SC_LOG_LEVEL_INFO:
+            return SDL_LOG_PRIORITY_INFO;
+        case SC_LOG_LEVEL_WARN:
+            return SDL_LOG_PRIORITY_WARN;
+        case SC_LOG_LEVEL_ERROR:
+            return SDL_LOG_PRIORITY_ERROR;
+        default:
+            assert(!"unexpected log level");
+            return SC_LOG_LEVEL_INFO;
+    }
+}
+
+
 int
 main(int argc, char *argv[]) {
 #ifdef __WINDOWS__
@@ -38,20 +56,23 @@ main(int argc, char *argv[]) {
     setbuf(stderr, NULL);
 #endif
 
-#ifndef NDEBUG
-    SDL_LogSetAllPriority(SDL_LOG_PRIORITY_DEBUG);
-#endif
-
     struct scrcpy_cli_args args = {
         .opts = SCRCPY_OPTIONS_DEFAULT,
         .help = false,
         .version = false,
     };
 
+#ifndef NDEBUG
+    args.opts.log_level = SC_LOG_LEVEL_DEBUG;
+#endif
+
     if (!scrcpy_parse_args(&args, argc, argv)) {
         return 1;
     }
 
+    SDL_LogPriority sdl_log = convert_log_level_to_sdl(args.opts.log_level);
+    SDL_LogSetAllPriority(sdl_log);
+
     if (args.help) {
         scrcpy_print_usage(argv[0]);
         return 0;