Implement preliminary OCaml support

[topolarity]

This is a preliminary implementation of OCaml compiler support in BinaryBuilder.

Dependent on JuliaPackaging/Yggdrasil#11146

[topolarity]

This looks to be almost working. There is some slight disagreement about darwinX in the target triples:

sandbox:${WORKSPACE}/srcdir # /opt/aarch64-apple-darwin/bin/ocamlopt.opt -v
The OCaml native-code compiler, version 5.4.0+dev2-2025-04-22
Standard library directory: /opt/aarch64-apple-darwin/bin/../lib/ocaml
sandbox:${WORKSPACE}/srcdir # ocamlopt.opt -v
/opt/bin/aarch64-apple-darwin20-libgfortran5-cxx11/ocamlopt.opt: line 5: /opt/aarch64-apple-darwin20/bin/ocamlopt.opt: No such file or directory

Any preference for how to resolve that?

[maleadt]

/opt/x86_64-linux-gnu/bin/../lib/gcc/x86_64-linux-gnu/5.2.0/../../../../x86_64-linux-gnu/bin/ld: /opt/x86_64-linux-gnu/bin/../lib/ocaml/stdlib.a(camlinternalFormatBasics.o): unrecognized relocation (0x2a) in section `.text.caml.camlCamlinternalFormatBasics$entry'
/opt/x86_64-linux-gnu/bin/../lib/gcc/x86_64-linux-gnu/5.2.0/../../../../x86_64-linux-gnu/bin/ld: final link failed: Bad value
collect2: error: ld returned 1 exit status

I guess this is because of using GCC 6 for building the shards (technically, OCaml only needs GCC 4.9+, but opam, one of the build tools I added to the shard, only builds on GCC 6 or later).

[maleadt]

Okay, this should be the first in the OCaml series (also including JuliaPackaging/BinaryBuilder.jl#1382 and JuliaPackaging/Yggdrasil#11146) that's ready for review, merge and tag. It's all fairly straightforward, only involving OCaml, with the exception of two broadly-impacting changes:

• preferred_gcc_version now defaults to nothing, indicating unspecifiedness, which I use to bump it from the default 4.8 to 6 when OCaml is requested. This because the OCaml compiler shards themselves are built using GCC v6.
• symlinks to wrappers are now also provided for host platform binaries, making it possible to switch to the host toolchain by doing PATH=/opt/bin/$host_full:/opt/$host/bin:$PATH. Before, there was no easy way to e.g. get a as that mapped to x86_64-linux-musl-as, which was problematic for my ocamlopt-based recipe that simply executes as.

[giordano]

So, I think this is ok, but I wanted to point out that we already do some shenanigans in gcc_version at

BinaryBuilderBase.jl/src/Rootfs.jl

Lines 447 to 538 in dd70539

	function gcc_version(p::AbstractPlatform,
	GCC_builds::Vector{GCCBuild},
	compilers::Vector{Symbol}=[:c];
	llvm_version::Union{Nothing,VersionNumber}=nothing)
	# First, filter by libgfortran version.
	if libgfortran_version(p) !== nothing
	GCC_builds = filter(b -> getabi(b).libgfortran_version == libgfortran_version(p), GCC_builds)
	end
	# Next, filter by libstdc++ GLIBCXX symbol version. Note that this
	# mapping is conservative; it is often the case that we return a
	# version that is slightly lower than what is actually installed on
	# a system. See https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html
	# for the whole list, as well as many other interesting factoids.
	if libstdcxx_version(p) !== nothing
	GCC_builds = filter(b -> getabi(b).libstdcxx_version <= libstdcxx_version(p), GCC_builds)
	end
	# Finally, enforce cxxstring_abi guidelines. It is possible to build
	# :cxx03 binaries on GCC 5+, (although increasingly rare) so the only
	# filtering we do is that if the platform is explicitly :cxx11, we
	# disallow running on < GCC 5.
	if cxxstring_abi(p) === "cxx11"
	GCC_builds = filter(b -> getversion(b) >= v"5", GCC_builds)
	end
	# LLVMBootstrap 12 needs to be built with GCCBootstrap ≥ 7, see
	# <https://github.com/JuliaPackaging/BinaryBuilderBase.jl/pull/112#issuecomment-776940748>.
	# However, when building for FreeBSD with LLVMBootstrap 12 we can't use `ld` from
	# binutils < 2.26 (which corresponds to GCCBootstrap < 6) to link some object files, see
	# <https://github.com/JuliaPackaging/BinaryBuilderBase.jl/issues/158>. The solution is
	# to not allow old GCCBootstrap with new versions of LLVMBootstrap for FreeBSD.
	if llvm_version !== nothing && Sys.isfreebsd(p) && llvm_version ≥ v"12"
	GCC_builds = filter(b -> getversion(b) ≥ v"6", GCC_builds)
	end
	# We don't have GCC 8 or older for FreeBSD 14.1+ on AArch64
	if Sys.isfreebsd(p) && arch(p) == "aarch64"
	GCC_builds = filter(b -> getversion(b) ≥ v"9", GCC_builds)
	end
	# We only use GCC 14 or newer for riscv64.
	if arch(p) == "riscv64"
	GCC_builds = filter(b -> getversion(b) ≥ v"14", GCC_builds)
	end
	# Rust on Windows requires binutils 2.25 (it invokes `ld` with `--high-entropy-va`),
	# which we bundle with GCC 5.
	# Rust requires glibc 2.17 (https://blog.rust-lang.org/2022/08/01/Increasing-glibc-kernel-requirements.html),
	# which we only use for GCC >5
	if :rust in compilers
	GCC_builds = filter(b -> getversion(b) ≥ v"5", GCC_builds)
	end
	# Msan uses clang, which emits R_X86_64_REX_GOTPCRELX, and thus requires
	# binutils >= 2.26.
	if sanitize(p) in ("memory", "memory_origins", "address")
	GCC_builds = filter(b -> getversion(b) ≥ v"6", GCC_builds)
	end
	# Filter the possible GCC versions depending on the microarchitecture
	if march(p) in ("avx", "avx2", "neonvfpv4")
	# "sandybridge", "haswell", "cortex-a53" introduced in GCC v4.9.0:
	# https://www.gnu.org/software/gcc/gcc-4.9/changes.html
	GCC_builds = filter(b -> getversion(b) >= v"4.9", GCC_builds)
	elseif march(p) in ("power9",)
	# "power9" introduced in GCC v6.1:
	# https://www.gnu.org/software/gcc/gcc-6/changes.html
	GCC_builds = filter(b -> getversion(b) >= v"6.1", GCC_builds)
	elseif march(p) in ("avx512", "armv8_1")
	# "thunderx2t99" introduced in GCC v7.1:
	# <https://www.gnu.org/software/gcc/gcc-7/changes.html>.
	# "skylake-avx512" introduced in GCC v6.1, but header files were broken
	# in that release:
	# <https://github.com/JuliaPackaging/Yggdrasil/pull/4485#issuecomment-1048226993>
	# <https://github.com/JuliaPackaging/Yggdrasil/pull/6392#discussion_r1138808437>.
	GCC_builds = filter(b -> getversion(b) >= v"7.1", GCC_builds)
	elseif march(p) in ("armv8_2_crypto",)
	# `cortex-a76` target introduced in GCC v9.1:
	# https://www.gnu.org/software/gcc/gcc-9/changes.html
	GCC_builds = filter(b -> getversion(b) >= v"9.1", GCC_builds)
	elseif march(p) in ("a64fx",)
	# `a64fx` target introduced in GCC v10.3:
	# https://www.gnu.org/software/gcc/gcc-10/changes.html
	GCC_builds = filter(b -> getversion(b) >= v"10.3", GCC_builds)
	elseif march(p) in ("apple_m1",)
	# At the moment we can only target this CPU with GCC 12
	GCC_builds = filter(b -> getversion(b) >= v"12", GCC_builds)
	end
	return getversion.(GCC_builds)
	end

for example in certain cases we change the version of the gcc toolchain based on the...llvm toolchain. I was never proud of that mess though.

[maleadt]

Let's merge this once CI is tagged. IIUC I also have to do a version bump, since BinaryBuilder.jl doesn't contain a committed Manifest (and we want JuliaPackaging/BinaryBuilder.jl#1382 to actually test OCaml support).