Handle absolute paths in typegen #5077

Job	Run time
build-rewatch (macos-13, x86_64-apple-darwin)	21s
build-compiler (ubuntu-latest, ocaml-variants.5.2.0+options,ocaml-option-static, true, true, true...	1m 11s
build-rewatch (macos-14, aarch64-apple-darwin)	16s
build-compiler (buildjet-2vcpu-ubuntu-2204-arm, ocaml-variants.5.2.0+options,ocaml-option-static,...	2m 8s
build-compiler (macos-13, 5.2.0, true)	2m 35s
build-rewatch (ubuntu-latest, x86_64-unknown-linux-musl)	12s
build-compiler (macos-14, 5.2.0, true)	1m 32s
build-compiler (windows-latest, 5.2.0, true)	2m 21s
build-rewatch (buildjet-2vcpu-ubuntu-2204-arm, aarch64-unknown-linux-musl)	13s
build-compiler (ubuntu-latest, ocaml-variants.5.0.0+options,ocaml-option-static)	1m 1s
build-rewatch (windows-latest, x86_64-pc-windows-gnu)	30s
build-compiler (ubuntu-latest, ocaml-variants.4.14.2+options,ocaml-option-static)	1m 10s
build-compiler (ubuntu-latest, ocaml-variants.4.13.0+options,ocaml-option-static)	1m 9s
package	0s
installationTest	0s
publish	0s
	14m 39s

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