Avoid hardcoding max fd size

Android changed max fd limit to 32768 since Android 9:
cb5fccc83c

Co-authored-by: LoveSy <shana@zju.edu.cn>

native/src/core/zygisk/hook.cpp

@@ -1,4 +1,5 @@
 #include <sys/mount.h>
+#include <sys/resource.h>
 #include <dlfcn.h>
 #include <unwind.h>
 #include <span>
@@ -217,6 +218,7 @@ DCL_HOOK_FUNC(static int, pthread_attr_destroy, void *target) {
 
 ZygiskContext::ZygiskContext(JNIEnv *env, void *args) :
     env(env), args{args}, process(nullptr), pid(-1), flags(0), info_flags(0),
+    allowed_fds([] static { rlimit r{32768, 32768}; getrlimit(RLIMIT_NOFILE, &r); return r.rlim_max; }()),
     hook_info_lock(PTHREAD_MUTEX_INITIALIZER) { g_ctx = this; }
 
 ZygiskContext::~ZygiskContext() {