install ocaml in dockerfile instead of postCreate.sh #9467

Job	Run time
test-devcontainer	13m 54s
build-compiler (macos-15-intel, 5.3.0, true, darwin-x64, x86_64-apple-darwin)	10m 26s
build-compiler (macos-15, 5.3.0, true, darwin-arm64, aarch64-apple-darwin)	6m 13s
build-compiler (ubuntu-24.04, ocaml-variants.5.0.0+options,ocaml-option-static, linux-x64, x86_64...	5m 3s
build-compiler (ubuntu-24.04, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, linux...	5m 16s
build-compiler (windows-2025, 5.3.0, true, win32-x64, x86_64-pc-windows-gnu, .exe)	10m 50s
build-compiler (ubuntu-24.04-arm, ocaml-variants.5.3.0+options,ocaml-option-static, true, true, t...	5m 39s
pkg-pr-new	49s
api-docs	13s
test-installation-npm (macos-15-intel)	25s
test-installation-pnpm (windows-2025)	38s
test-installation-pnpm (macos-15)	21s
test-integration-rewatch (ubuntu-24.04-arm)	2m 17s
test-integration-rewatch (macos-15-intel)	2m 27s
test-installation-pnpm (macos-15-intel)	25s
test-installation-pnpm (ubuntu-24.04-arm)	15s
test-installation-pnpm (ubuntu-24.04)	11s
test-installation-npm (ubuntu-24.04)	17s
test-integration-rewatch (ubuntu-24.04)	2m 19s
test-installation-npm (windows-2025)	59s
test-installation-npm (ubuntu-24.04-arm)	15s
test-integration-rewatch (windows-2025)	2m 16s
test-integration-rewatch (macos-15)	2m 21s
test-installation-npm (macos-15)	21s
publish	1s
	1h 14m 11s

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