Systhreads synchronizations use pthread functions

In the case where the two names already have the same canonical, we
don't need to update anything, but we do still need to get the coercion
right.

64235a3 flambda-backend: Change Float.nan from sNaN to qNaN (ocaml#466)
14a8e27 flambda-backend: Track GC work for all managed bigarray allocations (upstream 11022) (ocaml#569)
c3cda96 flambda-backend: Add two new methods to targetint for dwarf (ocaml#560)
e6f1fed flambda-backend: Handle arithmetic overflow in select_addr (ocaml#570)
dab7209 flambda-backend: Add Target_system to ocaml/utils (ocaml#542)
82d5044 flambda-backend: Enhance numbers.ml with more primitive types (ocaml#544)
216be99 flambda-backend: Fix flambda_o3 and flambda_oclassic attributes (ocaml#536)
4b56e07 flambda-backend: Test naked pointer root handling (ocaml#550)
40d69ce flambda-backend: Stop local function optimisation from moving code into function bodies; opaque_identity fixes for class compilation (ocaml#537)
f08ae58 flambda-backend: Implemented inlining history and use it inside inlining reports (ocaml#365)
ac496bf flambda-backend: Disable the local keyword in typing (ocaml#540)
7d46712 flambda-backend: Bugfix for Typedtree generation of arrow types (ocaml#539)
61a7b47 flambda-backend: Insert missing page table check in roots_nat.c (ocaml#541)
323bd36 flambda-backend: Compiler error when -disable-all-extensions and -extension are used (ocaml#534)
d8956b0 flambda-backend: Persistent environment and reproducibility (ocaml#533)
4a0c89f flambda-backend: Revert "Revert bswap PRs (480 and 482)" (ocaml#506)
7803705 flambda-backend: Cause a C warning when CAMLreturn is missing in C stubs. (ocaml#376)
6199db5 flambda-backend: Improve unboxing during cmm for Flambda (ocaml#295)
96b9e1b flambda-backend: Print diagnostics at runtime for Invalid (ocaml#530)
42ab88e flambda-backend: Disable bytecode compilers in ocamltest (ocaml#504)
58c72d5 flambda-backend: Backport ocaml#10595 from upstream/trunk (ocaml#471)
1010539 flambda-backend: Use C++ name mangling convention (ocaml#483)
81881bb flambda-backend: Local allocation test no longer relies on lifting (ocaml#525)
f5c4719 flambda-backend: Fix an assertion in Closure that breaks probes (ocaml#505)
c2cf2b2 flambda-backend: Add some missing command line arguments to ocamlnat (ocaml#499)

git-subtree-dir: ocaml
git-subtree-split: 64235a3

Co-authored-by: tmattio <tmattio@users.noreply.github.com>