[ASAN] heap-use-after-free in SpinLockTest.correctness test case

[JoeLoser]

Running Address Sanitizer on the locks_test test executable led to:

SUMMARY: AddressSanitizer: heap-use-after-free in folly::SingletonThreadLocal<folly::ThreadLocalPRNG::operator()()::Wrapper, folly::(anonymous namespace)::RandomTag, folly::detail::DefaultMake<folly::ThreadLocalPRNG::operator()()::Wrapper> >::Wrapper::~Wrapper()
Shadow bytes around the buggy address:
  0x1c08000003b0: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x1c08000003c0: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x1c08000003d0: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x1c08000003e0: fa fa fd fd fd fd fd fd fa fa fd fd fd fd fd fd
  0x1c08000003f0: fa fa 00 00 00 00 00 00 fa fa fd fd fd fd fd fd
=>0x1c0800000400: fa fa fd[fd]fd fd fd fa fa fa 00 00 00 00 00 fa
  0x1c0800000410: fa fa 00 00 00 00 00 fa fa fa fa fa fa fa fa fa
  0x1c0800000420: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0800000430: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0800000440: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0800000450: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb

How to reproduce:
Simply set -fsanitize=address to cxx and link flags for that target, build, and run the locks_test text executable. Setting -fno-omit-frame-pointer to cxx flags would be helpful too.