Make fstat work on file descriptor with no name

Author: hoodmane

src/library_syscall.js

@@ -680,7 +680,7 @@ var SyscallsLibrary = {
   },
   __syscall_fstat64: (fd, buf) => {
     var stream = SYSCALLS.getStreamFromFD(fd);
-    return SYSCALLS.doStat(FS.stat, stream.path, buf);
+    return SYSCALLS.doStat(stream.node.node_ops.getattr, stream.node, buf);
   },
   __syscall_fchown32: (fd, owner, group) => {
     FS.fchown(fd, owner, group);

test/fs/test_stat_unnamed_file_descriptor.c

@@ -0,0 +1,16 @@
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <assert.h>
+#include "stdio.h"
+
+int main() {
+    int fd = open("file.txt", O_RDWR | O_CREAT, 0666);
+    unlink("file.txt");
+    int res;
+    struct stat buf;
+    res = fstat(fd, &buf);
+    assert(res == 0);
+    assert(buf.st_atime > 1000000000);
+    printf("success\n");
+}