view_compiler.cpp: clean up file descriptor handling

view_compiler.cpp: clean up file descriptor handling

For file descriptors which are explicitly passed across an exec()
boundary, mark them as // NOLINT(android-cloexec-open). This suppresses
clang-tidy link checks (intended to be added as part of b/129350825)

Don't call close(STDOUT_FILENO). The dup2() syscall atomically closes
this for us, so we don't need to do it ourselves. Additionally, this
also fixes a race condition where another thread may call open() and get
an FD corresponding to STDOUT_FILENO, which we will then close as part
of the dup2() call. Removing the close() makes file descriptor handling
atomic.

Set O_CLOEXEC on outfd. The pre-duped file descriptor should have
O_CLOEXEC set on it. Calling dup2() will dup the file descriptor, but
NOT preserve the O_CLOEXEC flag. Quoting "man dup2":

  The two file descriptors do not share file descriptor flags
  (the close-on-exec flag).  The close-on-exec flag (FD_CLOEXEC;
  see fcntl(2)) for the duplicate descriptor is off.

If we don't set the O_CLOEXEC flag on outfd, we'll be leaking the file
descriptor twice, once as STDOUT_FILENO, and once as outfd. The second
leak is undesirable although harmless.

Additional cleanup: Add missing newlines at end of file.

Bug: 129350825
Test: compiles
Change-Id: Ic83ad72ef8a38106ad95ec0202c5c09c61fcf3e7