tcc: Explicitly require -l<lib> for libraries

Previously it was possible to specify e.g. -q<lib> and still link with
lib. Avoid such behaviour by checking for '-l' instead of '-l.'

tcc.c

@@ -474,7 +474,7 @@ int main(int argc, char **argv)
         const char *filename;
 
         filename = files[i];
-        if (filename[0] == '-' && filename[1]) {
+        if (filename[0] == '-' && filename[1] == 'l') {
             if (tcc_add_library(s, filename + 2) < 0) {
                 error_noabort("cannot find %s", filename);
                 ret = 1;