[CLI] "@" character removed when it's first path character with --build

### 🔎 Search Terms

"cli", "tsc", "build mode", "path"

### 🕗 Version & Regression Information

- This changed between versions 3.0 and 3.1 (LOL) and continue to 5.9.2

### ⏯ Playground Link

https://github.com/GongT/issues/tree/typescript-path-at-char

### 💻 Code

```bash
# all this is ok
tsc -p @scoped/package/src
tsc -b xxx@yyy/package/src
cd @scoped ; tsc -p package/src

# this is not
tsc -b @scoped/package/src
```

### 🙁 Actual behavior

error TS5083: Cannot read file 'scoped/package/src'.

### 🙂 Expected behavior

It should read `@scoped/package/src(/tsconfig.json)`

### Additional information about the issue

_No response_

Start by reproducing the reported behavior with `tsc -b @scoped/package/src`, then compare it with the working `tsc -p @scoped/package/src` cases. The fix is done when build mode preserves the leading `@` and reads `@scoped/package/src/tsconfig.json` as expected.

Written by the indexing model from the issue text.