compiler: fix stack overflow when creating recursive pointer types

There were two types that could result in a compiler stack overflow.
This is difficult to fix in LLVM 14, so I won't even bother. However,
this is trivial to fix with opaque pointers in LLVM 15. Therefore, this
fix is for LLVM 15 only.

Fixes: https://github.com/tinygo-org/tinygo/issues/3341

compiler/testdata/basic.ll

@@ -7,6 +7,8 @@ target triple = "wasm32-unknown-wasi"
 %main.kv.0 = type { i8, i32, i32, i32 }
 
 @main.kvGlobal = hidden global %main.kv zeroinitializer, align 4
+@main.a = hidden global { ptr, i32, i32 } zeroinitializer, align 4
+@main.b = hidden global [2 x ptr] zeroinitializer, align 4
 
 declare noalias nonnull ptr @runtime.alloc(i32, ptr, ptr) #0