[Continuation] Fix GCC 14 builds by adding __attribute__(noipa)

Turns out, 410cd9d1 ("[Continuation] Fix setJmp() by adding 'rax'
to clobber list") was not enough for GCC 14 (probably newer
ones). This time, the compiler (GCC 14.2.0) also failed to re-load
%rax after the setJmp() and also seemed to perform optimizations based
on the assumption that setJmp() would *always* return 0.

It appears

asm("nop" ::: "rax", "rbx", "r12", "r13", "r14", "r15", "memory");

in Continuation::setJmp() is now, after we added the 'noipa'
attribute, also no longer necessary. But we keep it for now.

emper/Continuation.hpp

@@ -37,7 +37,7 @@ class Continuation {
 	};
 
 	inline __attribute__((always_inline, returns_twice)) uintptr_t setJmp() {
-		auto set_rip = [](Continuation *c) __attribute__((noinline, hot, optimize(3))) {
+		auto set_rip = [](Continuation *c) __attribute__((noipa, noinline, hot, optimize(3))) {
 			c->ip = __builtin_return_address(0);
 			return 0;
 		};