Do our own fork/exec rather than using a library. This leads to
many improvements:
- unite the output recording path with the other path
- never concatenate arguments with spaces
- never use the shell
- move setexeccon after fork, so we don't need to take the lock
- general code refactor while we're there
My tests:
- Ensure Marlin device boots and vold_prepare_subdirs is called
successfully
- Try adb shell sm set-virtual-disk true, see that eg sgdisk output is
logged.
weilongping@huawei.com's tests:
- unlock a user's de and ce directory;
- connect to a OTG storage device or a sdcard and ensure the mount logic be successful
Bug: 26735063
Bug: 113796163
Test: details in commit
Change-Id: I0976413529d7cbeebf5b8649660a385f9b036f04
de2d6201ab