[PATCH] [Bug #21629] Enable `nonstring` attribute on clang 21

	[PATCH] [Bug #21629] Initialize `struct RString`

	[PATCH] [Bug #21629] Initialize `struct RArray`

	Suppress gcc 15 unterminated-string-initialization warnings

	Drop an ignored attribute
	MIME-Version: 1.0
	Content-Type: text/plain; charset=UTF-8
	Content-Transfer-Encoding: 8bit

	GCC 13.3.0 (Ubuntu 24.04) emits the following warning:

	../symbol.c: In function ‘rb_id_attrset’:
	../symbol.c:175:9: warning: ‘nonstring’ attribute ignored on objects of type ‘const char[][8]’ [-Wattributes]
	  175 |         RBIMPL_ATTR_NONSTRING() static const char id_types[][8] = {
	      |         ^~~~~~~~~~~~~~~~~~~~~

	Separate `__has_attribute` from `defined(__has_attribute)`

	Fix Visual C warnings:
	```
	regenc.h(121): warning C4067: unexpected tokens following preprocessor directive - expected a newline
	```

	Cast up `int` instruction code to `VALUE`

	Fix Visual C warnings:
	```
	iseq.c(3793): warning C4312: 'type cast': conversion from 'int' to 'void *' of greater size
	iseq.c(3794): warning C4312: 'type cast': conversion from 'int' to 'void *' of greater size
	```

	Do not let files depend on a phony target

	Detect `clock_gettime` and `clock_getres` for winpthreads

Fix crash when checking symbol encoding

	[Bug #20245]

	We sometimes pass in a fake string to sym_check_asciionly. This can crash
	if sym_check_asciionly raises because it creates a CFP with the fake
	string as the receiver which will crash if GC tries to mark the CFP.

	For example, the following script crashes:

	    GC.stress = true
	    Object.const_defined?("\xC3")

when the RUBY_FREE_ON_SHUTDOWN environment variable is set, manually free memory at shutdown.

Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
Co-authored-by: Peter Zhu <peter@peterzhu.ca>

[Feature #19425]

* Implement optimize send in yjit

This successfully makes all our benchmarks exit way less for optimize send reasons.
It makes some benchmarks faster, but not by as much as I'd like. I think this implementation
works, but there are definitely more optimial arrangements. For example, what if we compiled
send to a jump table? That seems like perhaps the most optimal we could do, but not obvious (to me)
how to implement give our current setup.

Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>

* Attempt at fixing the issues raised by @XrXr

* fix allowlist

* returns 0 instead of nil when not found

* remove comment about encoding exception

* Fix up c changes

* Update assert

Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>

* get rid of unneeded code and fix the flags

* Apply suggestions from code review

Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>

* rename and fix typo

Co-authored-by: Alan Wu <XrXr@users.noreply.github.com>