dynamic tls tests broken with glibc 2.25

[kcc]

People start complaining about glibc 2.25 breaking the sanitizers.
https://bugs.llvm.org/show_bug.cgi?id=36065
https://bugs.llvm.org/show_bug.cgi?id=36326

I don't have cycles to work on this, volunteers welcome.

If anyone here from glibc, https://sourceware.org/glibc/wiki/ThreadPropertiesAPI is still relevant.

[chefmax]

Seems to be caused by this: https://sourceware.org/bugzilla/show_bug.cgi?id=17730

[chefmax]

Perhaps we just need something like DTLS_on_libc_memalign for malloc, but I'm not sure, this needs testing.

[kcc]

I've pinged the glibc folks here: https://sourceware.org/ml/libc-alpha/2018-02/msg00567.html

[Lekensteyn]

All 32-bit applications currently crash with glibc 2.27, I have reported a new issue for this here: #954

[thurstond]

"Fix tls_get_addr handling for glibc >=2.25" (https://reviews.llvm.org/D147459) landed in LLVM upstream last Friday, which should fix the issue.