minijail: add default ret log build-time option

Having an option to impose SECCOMP_RET_LOG by default at
build time is very useful while debugging or rolling out
toolchain or libc upgrades, to be able to see and fix as
many seccomp filter failures at runtime without adding
-L to each invocation or fixing crashes one by one.

BUG: 187795855
TEST: Local builds; CQ

Change-Id: I4c853edbf4b3d2798f95d6b42eb7a765be6209e9
diff --git a/util.h b/util.h
index 359ce95..6c5ed9d 100644
--- a/util.h
+++ b/util.h
@@ -144,6 +144,14 @@
 #endif
 }
 
+static inline bool seccomp_default_ret_log(void) {
+#if defined(SECCOMP_DEFAULT_RET_LOG)
+	return true;
+#else
+	return false;
+#endif
+}
+
 static inline size_t get_num_syscalls(void)
 {
 	return syscall_table_size;