deduplicate_flags() split flags on whitespace then ran a per-token
unique. For paired flags like `-Xclang -mllvm` or `-framework Cocoa`,
where the value is a separate token, the value token could collide
with an unrelated flag or value and get dropped, corrupting the
command line.
Group known paired flags (-Xclang, -Xpreprocessor, -Xlinker,
-Xassembler, -framework, -arch, -target, -include, -imacros, -isystem,
-isysroot, -iquote, -idirafter, -MT, -MF, -MQ) with their following
token into a single atom before the unique pass.
Switch the rust and go_win downloaders from baking PKG_ROOT_PATH into
the extract path at download time to the {pkg_root_path} template,
which ArtifactExtractor resolves at extract time. This keeps the path
stable across runs where pkg_root_path differs between download and
extract (e.g. containerised vs host builds).
The shell invocation runs `$CXX -c` to compile watcher-c.cpp to a .o,
which never links. Passing linker flags to a compile-only step is
either ignored or, with some flags, an error. Drop them.
ax_gcc_archflag has no Zen cpuid pattern and falls back to
-mtune=amdfam10, which under LLVM+LTO emits SSE4a extrq and SIGILLs on
Intel hosts. Disable the implicit --with-gcc-arch so host CPU features
do not bleed into the built binaries.
vswhere.exe defaults to searching Community, Professional, and
Enterprise editions only. CI environments typically install the
lightweight Build Tools product which is a separate product type
(Microsoft.VisualStudio.Product.BuildTools). Without -products *
the tool returns no results and the build fails with "Visual Studio
with C++ tools not found".
See: https://github.com/microsoft/vswhere/wiki/Find-MSBuild
