is rootDirs support?

```
.
├── package.json
├── src
│ ├── index.ts
├── tsconfig.json
└── tt
├── a
│ └── aa.ts
└── b
└── bb.ts
```

my tsconfig.json
```json
{
"$schema": "https://json.schemastore.org/tsconfig",
"compilerOptions": {
"isolatedModules": true,
"resolveJsonModule": true,
"allowSyntheticDefaultImports": true,
"declaration": true,
"declarationMap": false,
"esModuleInterop": true,
"module": "commonjs",
"moduleResolution": "node",
"pretty": true,
"strict": true,
"incremental": false,
"target": "es2021",
"baseUrl": ".",
"lib": ["es2021"],
"outDir": "./dist",
"rootDir": ".",
"skipLibCheck": true,
"forceConsistentCasingInFileNames": true,
"rootDirs": [
"src",
"tt/b",
"tt/a"
]
},
"include": ["src", "__tests__/**/*.ts", "tt"],
"exclude": ["node_modules"]
}
```

```
// src/index.ts
import { b } from "./bb";
console.log(b);

// tt/a/aa.ts
export const a = 1;

// tt/b/bb.ts
import { a } from "./aa";
console.log(a);
export const b = 2;
```

while running `tsup --watch`

it errors

```
✘ [ERROR] Could not resolve "./bb"

src/index.ts:1:18:
1 │ import { b } from "./bb";
╵ ~~~~~~

ESM Build failed
Error: Build failed with 1 error:
src/index.ts:1:18: ERROR: Could not resolve "./bb"
at failureErrorWithLog (/Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:1575:15)
at /Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:1033:28
at runOnEndCallbacks (/Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:1447:61)
at buildResponseToResult (/Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:1031:7)
at /Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:1143:14
at responseCallbacks. (/Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:680:9)
at handleIncomingPacket (/Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:735:9)
at Socket.readFromStdout (/Users/silentlee/Desktop/eslint-config-bnc/node_modules/.pnpm/esbuild@0.15.18/node_modules/esbuild/lib/main.js:656:7)
at Socket.emit (node:events:527:28)
at addChunk (node:internal/streams/readable:315:12)
✘ [ERROR] Could not resolve "./bb"

src/index.ts:1:18:
1 │ import { b } from "./bb";
╵ ~~~~~~

CJS Build failed
```

with `./node_modules/.bin/tsc --traceResolution | grep -A 41 "======== Resolving module './bb'" --color=auto`
```
======== Resolving module './bb' from '/Users/silentlee/Desktop/eslint-config-bnc/src/index.ts'. ========
Explicitly specified module resolution kind: 'NodeJs'.
'rootDirs' option is set, using it to resolve relative module name './bb'.
Checking if '/Users/silentlee/Desktop/eslint-config-bnc/src/' is the longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/src/bb' - 'true'.
Checking if '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/' is the longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/src/bb' - 'false'.
Checking if '/Users/silentlee/Desktop/eslint-config-bnc/tt/a/' is the longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/src/bb' - 'false'.
Longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/src/bb' is '/Users/silentlee/Desktop/eslint-config-bnc/src/'.
Loading 'bb' from the root dir '/Users/silentlee/Desktop/eslint-config-bnc/src/', candidate location '/Users/silentlee/Desktop/eslint-config-bnc/src/bb'.
Loading module as file / folder, candidate module location '/Users/silentlee/Desktop/eslint-config-bnc/src/bb', target file type 'TypeScript'.
File '/Users/silentlee/Desktop/eslint-config-bnc/src/bb.ts' does not exist.
File '/Users/silentlee/Desktop/eslint-config-bnc/src/bb.tsx' does not exist.
File '/Users/silentlee/Desktop/eslint-config-bnc/src/bb.d.ts' does not exist.
Directory '/Users/silentlee/Desktop/eslint-config-bnc/src/bb' does not exist, skipping all lookups in it.
Trying other entries in 'rootDirs'.
Loading 'bb' from the root dir '/Users/silentlee/Desktop/eslint-config-bnc/tt/b', candidate location '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/bb'.
Loading module as file / folder, candidate module location '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/bb', target file type 'TypeScript'.
File '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/bb.ts' exist - use it as a name resolution result.
======== Module name './bb' was successfully resolved to '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/bb.ts'. ========
======== Resolving module './aa' from '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/bb.ts'. ========
Explicitly specified module resolution kind: 'NodeJs'.
'rootDirs' option is set, using it to resolve relative module name './aa'.
Checking if '/Users/silentlee/Desktop/eslint-config-bnc/src/' is the longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa' - 'false'.
Checking if '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/' is the longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa' - 'true'.
Checking if '/Users/silentlee/Desktop/eslint-config-bnc/tt/a/' is the longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa' - 'false'.
Longest matching prefix for '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa' is '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/'.
Loading 'aa' from the root dir '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/', candidate location '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa'.
Loading module as file / folder, candidate module location '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa', target file type 'TypeScript'.
File '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa.ts' does not exist.
File '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa.tsx' does not exist.
File '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa.d.ts' does not exist.
Directory '/Users/silentlee/Desktop/eslint-config-bnc/tt/b/aa' does not exist, skipping all lookups in it.
Trying other entries in 'rootDirs'.
Loading 'aa' from the root dir '/Users/silentlee/Desktop/eslint-config-bnc/src', candidate location '/Users/silentlee/Desktop/eslint-config-bnc/src/aa'.
Loading module as file / folder, candidate module location '/Users/silentlee/Desktop/eslint-config-bnc/src/aa', target file type 'TypeScript'.
File '/Users/silentlee/Desktop/eslint-config-bnc/src/aa.ts' does not exist.
File '/Users/silentlee/Desktop/eslint-config-bnc/src/aa.tsx' does not exist.
File '/Users/silentlee/Desktop/eslint-config-bnc/src/aa.d.ts' does not exist.
Directory '/Users/silentlee/Desktop/eslint-config-bnc/src/aa' does not exist, skipping all lookups in it.
Loading 'aa' from the root dir '/Users/silentlee/Desktop/eslint-config-bnc/tt/a', candidate location '/Users/silentlee/Desktop/eslint-config-bnc/tt/a/aa'.
Loading module as file / folder, candidate module location '/Users/silentlee/Desktop/eslint-config-bnc/tt/a/aa', target file type 'TypeScript'.
File '/Users/silentlee/Desktop/eslint-config-bnc/tt/a/aa.ts' exist - use it as a name resolution result.
======== Module name './aa' was successfully resolved to '/Users/silentlee/Desktop/eslint-config-bnc/tt/a/aa.ts'. ========
```
and it can build succeed with `tsc`

Reproduce the failure with tsup --watch using tsconfig.json, src/index.ts, tt/a/aa.ts, and tt/b/bb.ts, then compare it with the successful tsc resolution trace. Done means the tsup watch build resolves ./bb and ./aa through the configured rootDirs without the reported errors.

Written by the indexing model from the issue text.