Stale build_script

Couldn't figure out what was causing a syntax error in my build_script. Eventually commented out the entire file and still had a missing semicolon at line 11 haha

Some hopefully relevant excerpt from my build.ninja:
```
rule build_script
command = ${ocamlc} unix.cma ${linked_internals} ${refmt} -open Bsb_internals -o ${out} ${impl} ${in}
description = ^[[34mBuilding^[[39m ^[[2m${out}^[[22m
build /Users/schmave/Documents/git/testuv/lib/bs/native/build_script.exe : build_script /Users/schmave/Documents/git/testuv/lib/bs/native/build_script.re || src/Example.mlast.d src/Http.mlast.d
linked_internals = $linked_internals -I /Users/schmave/Documents/git/testuv/node_modules/bs-platform/lib /Users/schmave/Documents/git/testuv/node_modules/bs
refmt = -pp "/Users/schmave/Documents/git/testuv/node_modules/bs-platform/lib/refmt.exe --print binary"
impl = -impl
rule run_build_script
command = /Users/schmave/Documents/git/testuv/lib/bs/native/build_script.exe /Users/schmave/Documents/git/testuv/node_modules/bs-platform/vendor /Users/schm
description = ^[[32mRunning^[[39m ^[[2m${out}^[[22m
build run_build_script : run_build_script || /Users/schmave/Documents/git/testuv/lib/bs/native/build_script.exe
```

As far as I can remember how to read ninja files, this seems to have the required dependency on `/Users/schmave/Documents/git/testuv/lib/bs/native/build_script.re` so I'm not sure what's up (probably what's up is my lack of ability to read ninja files).

Start by reproducing the syntax error from the generated build.ninja rules for build_script and run_build_script. Read lib/bs/native/build_script.re alongside the reported line 11 and verify how the build_script dependency is generated. Done means identifying why the error remains and confirming that the build completes without it.

Written by the indexing model from the issue text.