libpthread/nptl: create timer thread with sufficiant stack size (account for TLS)
Create timer thread with sufficiant stack size (take into account
allocated space for thread-local-storage), for this backport glibc
commit 'Create internal threads with sufficient stack size' ([1],
[2]) introducing __pthread_get_minstack() and use it in
__start_helper_thread().
Fixes timer_create() in case of linking with library using large
TLS area (e.g openblas, see [3]).
[1] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=2c1094bd700e63a8d7f547b3f5495bedb55c0a08
[2] https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=630f4cc3aa019ede55976ea561f1a7af2f068639
[3] http://lists.busybox.net/pipermail/buildroot/2021-April/308281.html
Signed-off-by: Peter Seiderer <ps.report@gmx.net>