Add prerequisite support for macOS - #183
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On targets where long double is IEEE quad (aarch64), vfprintf's `union arg` held the float value as long double, so `%f` (and the fmt_fp call) round-tripped double -> long double -> double through __extenddftf2/__trunctfdf2. That pulls libgcc (or compiler-rt) soft-float into every freestanding link that uses printf, even for integer-only formats. fmt_fp already takes a double, so the long double was pure overhead. Use double for the field; %L float conversions are treated as double (never used by OCaml unikernels). aarch64 cross unikernels now link with no libgcc at all (clang already inlines the atomics).
The aarch64 wrapper linked -lgcc for printf's long-double soft-float (now gone: printf formats as double) and for GCC's default outline atomics (-moutline-atomics lowers C11 atomics to __aarch64_* helpers in libgcc, which also pull __getauxval, absent on a freestanding solo5 target). Pass -mno-outline-atomics so atomics inline (LL/SC); the link then needs no compiler runtime, so drop -lgcc and let a pure-LLVM toolchain link aarch64 unikernels.
Add a new option so that the toolchain can invoke commands with an extended `PATH`
This CI workflow illustrates how this PR plays with changes from Solo5/solo5#656 and from mirage#177 It should be amended to follow updates on those other changes
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This PR proposes changes that are along the lines the ones in Solo5/solo5#656 to make adding support for macOS smoother.
At the moment this is a draft containing:
--path-prependconfigure optionARandRANLIBto build support librariesmanifest.cfor when solo5-elftool is not availableThis PR leaves to another PR discussions about the best way to package this.