env: correct sign for error code

Error codes should be negative.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

common/env_attr.c

@@ -153,7 +153,7 @@ static int regex_callback(const char *name, const char *attributes, void *priv)
 		}
 	} else {
 		printf("Error compiling regex: %s\n", slre.err_str);
-		retval = EINVAL;
+		retval = -EINVAL;
 	}
 done:
 	return retval;