player: prefer logical current directory path

The "PWD" enviornment variable is described by POSIX. We don't go to
length to verify its contents, but just trust it.

This affects the logic for resuming playback.

options/path.c

@@ -259,6 +259,10 @@ char *mp_path_join(void *talloc_ctx, const char *p1, const char *p2)
 
 char *mp_getcwd(void *talloc_ctx)
 {
+    char *e_wd = getenv("PWD");
+    if (e_wd)
+        return talloc_strdup(talloc_ctx, e_wd);
+
     char *wd = talloc_array(talloc_ctx, char, 20);
     while (getcwd(wd, talloc_get_size(wd)) == NULL) {
         if (errno != ERANGE) {