* Fixed memory leak from sigaltstack

…N) (ocaml#11095)

* [Minor] Clean-up some atomic casts

* Strengthen test

* Add an acquire fence after `young_limit` triggers an allocation failure

The output has been disassembled (gcc -O2, arch=x86-64) to confirm
that `CAMLunlikely` works as intended and produces equivalent code as
before.

* Reintroduce caml_update_young_limit

This function ensures that young_limit is always reset to its desired
value, without risk of race.

Also avoid relying on an information-carrying value for young_limit.

* Always reset young limit with dedicated function

Aim to take all requests into account to simplify reasoning

Reset young_limit after reinitialisation of interrupt variables

* [minor] Simplify assertion and make it clearer at least to me

(the absence of race in the assertion depended on who calls it)

`ranlib` seems unnecessary if a POSIX-compliant `ar` is used and time stamps are preserved when a `.a` file is installed.

…adunsafe

Document that Scanf is not thread-safe

Joining more than once on a domain no longer raises an exception.

…path

fix ocaml#9140 New flag creation `nocwd`

Make finaliser2 test deterministic

Simplify Domain.join

The Iload constructor was changed from a triple to a record, but the
disabled backends weren't updated.

Eliminates the partial match warning in these backends, but obviously
the emitters are still broken.

Unused variable r12 was originally removed in PR#502.

Extra parameter added in the multicore merge. Obviously the emitter
remains broken.

The i386 emitter still had the 4.x name.

The two labels were swapped.  

Fixes: ocaml#11202

Delay releasing joining domains

The test triggers a stack overflow in the type checker.  With the new
default max stack size, it takes forever to reach the overflow.

Co-authored-by: Florian Angeletti <[email protected]>

This had been forgotten in ocaml#11243

Guard additional uses of _MSC_VER to suppress undefined variable warnings

(cherry picked from commit 2c2e990)

Factors out some common usage between Warnings and Location for
zero-length ghost locations.

Load_path.find{,_uncap} now invoke a hook before raising Not_found,
which provides a mechanism for automatically adding directories to the
Load_path if required.

[1/3] Restructure LIBDIR: Move Dynlink, Str and Unix to sub-directories

Suggested-by: Guillaume Munch-Maccagnoni <[email protected]>
Suggested-by: David Allsopp <[email protected]>
Reviewed-by: KC Sivaramakrishnan <[email protected]>

protect Max_domains with CAML_INTERNALS

Before this commit, the -cmi-file option was recognized only by ocamlc.

This commit makes sure the option is also recognized by ocamlopt.

Make sure ocamlopt recognizes the -cmi-file command-line option

Makefile.config_if_required can be include'd more than once which
overrides any changes made to flags.

Co-authored-by: fabbing <[email protected]>

Ensure Makefile.build_config is only loaded once