tests: Skip const OOM tests on aarch64-unknown-linux-gnu

Skip const OOM tests on AArch64 Linux through explicit annotations
instead of inside opt-dist.
Intended to avoid confusion in cases like #135952.

Prerequisite for #135960.

Author: mrkajetanp

tests/ui/consts/large_const_alloc.rs

@@ -1,5 +1,7 @@
 //@ only-64bit
 // on 32bit and 16bit platforms it is plausible that the maximum allocation size will succeed
+// FIXME (#135952) In some cases on AArch64 Linux the diagnostic does not trigger
+//@ ignore-aarch64-unknown-linux-gnu
 
 const FOO: () = {
     // 128 TiB, unlikely anyone has that much RAM

tests/ui/consts/promoted_running_out_of_memory_issue-130687.rs

@@ -3,6 +3,8 @@
 
 // Needs the max type size to be much bigger than the RAM people typically have.
 //@ only-64bit
+// FIXME (#135952) In some cases on AArch64 Linux the diagnostic does not trigger
+//@ ignore-aarch64-unknown-linux-gnu
 
 pub struct Data([u8; (1 << 47) - 1]);
 const _: &'static Data = &Data([0; (1 << 47) - 1]);