Clean up ninja leftovers #9433

Job	Run time
test-devcontainer	4m 24s
build-compiler (ubuntu-24.04, ocaml-variants.5.0.0+options,ocaml-option-static, linux-x64, x86_64...	3m 25s
build-compiler (windows-2025, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu, .exe)	7m 11s
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	3m 26s
build-compiler (macos-15, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	4m 59s
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	3m 19s
build-compiler (macos-15-intel, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	8m 49s
api-docs	-1s
pkg-pr-new	-1s
test-integration-rewatch	-1s
test-installation-npm	-1s
test-installation-pnpm	-1s
publish	-1s
	35m 27s

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