[sanitizers] Update sanitizers test to better match glibc internals

Reapply 282061.

One of the tests relying on sem_t's layout gets the wrong value for versions of
glibc newer than 2.21 on platforms that don't have 64-bit atomics (e.g. ARM).

This commit fixes the test to work with:
* versions of glibc >= 2.21 on platforms with 64-bit atomics: unchanged
* versions of glibc >= 2.21 on platforms without 64-bit atomics: the semaphore
value is shifted by SEM_VALUE_SHIFT (which is set to 1 in glibc's internal
headers)
* versions of glibc < 2.21: unchanged

The logic is complicated a bit by the fact that the sanitizers always pick the
oldest version of the symbol available in glibc, which creates discrepancies
between old platforms which contain several versions od the sem_init symbol, and
newer platforms which contain only one.

See the glibc 2.23 sources:
* sysdeps/nptl/internaltypes.h (struct new_sem for glibc >= 2.21 and
                                struct old_sem for glibc < 2.21)
* nptl/sem_getvalue.c

This was uncovered on one of the new buildbots that we are trying to move to
production.

Differential Revision: https://reviews.llvm.org/D24766

llvm-svn: 283299