[sanitizer] Use size_t on g_tls_size to fix build on x32

On x32 size_t == unsigned int, not unsigned long int:

../../../../../src-master/libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cpp: In function ??void __sanitizer::InitTlsSize()??:
../../../../../src-master/libsanitizer/sanitizer_common/sanitizer_linux_libcdep.cpp:209:55: error: invalid conversion from ??__sanitizer::uptr*?? {aka ??long unsigned int*??} to ??size_t*?? {aka ??unsigned int*??} [-fpermissive]
  209 |   ((void (*)(size_t *, size_t *))get_tls_static_info)(&g_tls_size, &tls_align);
      |                                                       ^~~~~~~~~~~
      |                                                       |
      |                                                       __sanitizer::uptr* {aka long unsigned int*}

by using size_t on g_tls_size.  This is to fix:

https://bugs.llvm.org/show_bug.cgi?id=50332

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D102446