[ASan] Make the regression test for time(NULL) Linux-specific, as it crashes on Darwin (and the problem used to occur on Linux).
Do not use zero-based shadow for the time() test.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@182107 91177308-0d34-0410-b5e6-96231b3b80d8