dev-lang/ruby: avoid UB with coroutines for 4.0.x

Define RB_THREAD_CURRENT_EC_NOINLINE to always make a function call to
get the coroutine execution context. Without it, GCC 16's x86 CSE pass
will (with TLS descriptors at least) cache the value.

971174054a26be0a4becbe7c67a7cc980158abf2 added the convenient macro
in 4.0.0, so for older releases, we'll have to patch instead.

Bug: https://bugs.ruby-lang.org/issues/20243
Bug: https://gcc.gnu.org/PR124995
Closes: https://bugs.gentoo.org/972696
Signed-off-by: Sam James <sam@gentoo.org>

dev-lang/ruby/ruby-4.0.3-r1.ebuild

@@ -209,6 +209,8 @@ src_configure() {
 	append-flags -fno-strict-aliasing
 	# Fails to link (gcc PR124865, gcc PR50676)
 	filter-flags -flto-partition=cache
+	# bug #972696
+	append-cppflags -DRB_THREAD_CURRENT_EC_NOINLINE
 
 	# Workaround for bug #938302
 	if use systemtap && has_version "dev-debug/systemtap[-dtrace-symlink(+)]" ; then

dev-lang/ruby/ruby-4.0.9999.ebuild

@@ -209,6 +209,8 @@ src_configure() {
 	append-flags -fno-strict-aliasing
 	# Fails to link (gcc PR124865, gcc PR50676)
 	filter-flags -flto-partition=cache
+	# bug #972696
+	append-cppflags -DRB_THREAD_CURRENT_EC_NOINLINE
 
 	# Workaround for bug #938302
 	if use systemtap && has_version "dev-debug/systemtap[-dtrace-symlink(+)]" ; then