Add more time syscalls and fix touch command in busybox

[yunwei37]

Add more time syscalls

• Add more time related syscalls:
  • time( )
  • gettimeofday( )
  • gettusage( )
  • times( )
• update document for these syscalls
• unit test

note: these syscalls is not very complete, but support basic function of getting time ( the same in rCore ).

related: fix touch command

• use touch command in busybox, need to fix utimensat syscall
  • touch can create file successfully!
• update document
• test with busybox

sides

• add fcntl consts in linux-object
• add more test with current commands in busybox;

[coveralls]

Pull Request Test Coverage Report for Build 202045542

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 25 of 95 (26.32%) changed or added relevant lines in 3 files are covered.
• 45 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.2%) to 33.833%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
linux-syscall/src/lib.rs	0	5	0.0%
linux-syscall/src/time.rs	11	76	14.47%

Files with Coverage Reduction	New Missed Lines	%
linux-syscall/src/time.rs	4	15.66%
linux-object/src/fs/mod.rs	11	75.9%
linux-syscall/src/file/file.rs	30	43.86%

Totals
Change from base Build 201900295:	-0.2%
Covered Lines:	4289
Relevant Lines:	12677

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💛 - Coveralls