llvm: fix lowering of runtime refs to comptime-only decls

When we want a runtime pointer to a zero-bit value we use an undef
pointer, but what if we want a runtime pointer to a comptime-only value?
Normally, if `T` is a comptime-only type such as `*const comptime_int`,
then `*const T` would also be a comptime-only type, so anything
referencing a comptime-only value is usually also comptime-only, and
therefore not emitted to the executable.

However, what if instead we have a `*const anyopaque` pointing to a
comptime-only value?  Certainly, `*const anyopaque` is a runtime type,
and so we need some runtime value to store, even when it happens to be
pointing to a comptime-only value.  In this case we want to do the same
thing as we do when pointing to a zero-bit value, so we use
`hasRuntimeBits` to handle both cases instead of ignoring comptime.

Closes #12025

src/codegen/llvm.zig

@@ -4077,7 +4077,7 @@ pub const DeclGen = struct {
         }
 
         const is_fn_body = decl.ty.zigTypeTag() == .Fn;
-        if (!is_fn_body and !decl.ty.hasRuntimeBitsIgnoreComptime()) {
+        if (!is_fn_body and !decl.ty.hasRuntimeBits()) {
             return self.lowerPtrToVoid(tv.ty);
         }
 

test/behavior.zig

@@ -83,6 +83,7 @@ test {
     _ = @import("behavior/bugs/11213.zig");
     _ = @import("behavior/bugs/11816.zig");
     _ = @import("behavior/bugs/12003.zig");
+    _ = @import("behavior/bugs/12025.zig");
     _ = @import("behavior/bugs/12033.zig");
     _ = @import("behavior/bugs/12430.zig");
     _ = @import("behavior/bugs/12486.zig");

test/behavior/bugs/12025.zig

@@ -0,0 +1,10 @@
+test {
+    comptime var st = .{
+        .foo = &1,
+        .bar = &2,
+    };
+
+    inline for (@typeInfo(@TypeOf(st)).Struct.fields) |field| {
+        _ = field;
+    }
+}