microbundle out of memory on build

How to reproduce:
1. Clone https://github.com/daangn/urlpack
2. `cd urlpack/packages/msgpack` (https://github.com/daangn/urlpack/tree/main/packages/msgpack)
3. `yarn install`
4. `yarn _build` (`microbundle --format esm,cjs`)

This always fails with an out-of-memory issue. on Node v14, v16, Mac OS and Ubuntu 20.04

It is not reproduced in other packages with similar code and settings.

```
yarn run v1.22.5
$ microbundle --format esm,cjs

<--- Last few GCs --->

[44348:0x5519880] 13088 ms: Scavenge 3273.1 (3307.3) -> 3273.1 (3307.3) MB, 36.7 / 0.0 ms (average mu = 0.906, current mu = 0.894) allocation failure
[44348:0x5519880] 13243 ms: Scavenge 3536.7 (3570.9) -> 3536.7 (3570.9) MB, 36.9 / 0.0 ms (average mu = 0.906, current mu = 0.894) allocation failure
[44348:0x5519880] 13643 ms: Scavenge 3574.7 (3608.9) -> 3574.7 (3608.9) MB, 5.6 / 0.0 ms (average mu = 0.906, current mu = 0.894) allocation failure

<--- JS stacktrace --->

FATAL ERROR: MarkCompactCollector: young object promotion failed Allocation failed - JavaScript heap out of memory
1: 0xa222f0 node::Abort() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
2: 0x96411f node::FatalError(char const*, char const*) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
3: 0xb97f1e v8::Utils::ReportOOMFailure(v8::internal::Isolate*, char const*, bool) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
4: 0xb98297 v8::internal::V8::FatalProcessOutOfMemory(v8::internal::Isolate*, char const*, bool) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
5: 0xd52fd5 [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
6: 0xd83bbe v8::internal::EvacuateNewSpaceVisitor::Visit(v8::internal::HeapObject, int) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
7: 0xd8fbf6 v8::internal::FullEvacuator::RawEvacuatePage(v8::internal::MemoryChunk*, long*) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
8: 0xd7bd8f v8::internal::Evacuator::EvacuatePage(v8::internal::MemoryChunk*) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
9: 0xd7c008 v8::internal::PageEvacuationTask::RunInParallel(v8::internal::ItemParallelJob::Task::Runner) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
10: 0xd6e8e9 v8::internal::ItemParallelJob::Run() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
11: 0xd91b50 void v8::internal::MarkCompactCollectorBase::CreateAndExecuteEvacuationTasks(v8::internal::MarkCompactCollector*, v8::internal::ItemParallelJob*, v8::internal::MigrationObserver*, long) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
12: 0xd923ec v8::internal::MarkCompactCollector::EvacuatePagesInParallel() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
13: 0xd925b5 v8::internal::MarkCompactCollector::Evacuate() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
14: 0xda45b1 v8::internal::MarkCompactCollector::CollectGarbage() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
15: 0xd60878 v8::internal::Heap::MarkCompact() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
16: 0xd62368 v8::internal::Heap::CollectGarbage(v8::internal::AllocationSpace, v8::internal::GarbageCollectionReason, v8::GCCallbackFlags) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
17: 0xd642a5 v8::internal::Heap::HandleGCRequest() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
18: 0xd0a787 v8::internal::StackGuard::HandleInterrupts() [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
19: 0x107c20a v8::internal::Runtime_StackGuardWithGap(int, unsigned long*, v8::internal::Isolate*) [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
20: 0x1423279 [/home/cometkim/.asdf/installs/nodejs/14.17.0/bin/node]
Aborted (core dumped)
error Command failed with exit code 134.
```

Clone daangn/urlpack, enter packages/msgpack, run yarn install, then reproduce with yarn _build (microbundle --format esm,cjs). Read the package configuration and microbundle build path involved in this command; done means the msgpack package builds successfully without exhausting the Node.js heap on the reported environments.

Written by the indexing model from the issue text.