Restructure native codebase

native/jni/base/missing.hpp

@@ -0,0 +1,26 @@
+#pragma once
+
+#include <sys/syscall.h>
+#include <linux/fcntl.h>
+#include <unistd.h>
+#include <cerrno>
+#include <cstdio>
+
+static inline int sigtimedwait(const sigset_t* set, siginfo_t* info, const timespec* timeout) {
+    union {
+        sigset_t set;
+        sigset_t set64;
+    } s{};
+    s.set = *set;
+    return syscall(__NR_rt_sigtimedwait, &s.set64, info, timeout, sizeof(sigset64_t));
+}
+
+static inline int fexecve(int fd, char* const* argv, char* const* envp) {
+    syscall(__NR_execveat, fd, "", argv, envp, AT_EMPTY_PATH);
+    if (errno == ENOSYS) {
+        char buf[256];
+        std::snprintf(buf, sizeof(buf), "/proc/self/fd/%d", fd);
+        execve(buf, argv, envp);
+    }
+    return -1;
+}