Windows Dev Kit: ability for it to upgrade itself

[ehaas]

Ran into this building Zig on Windows using the compiler dev kit tarball, on a system that does have MSVC installed (not sure if that matters)

According to git bisect the problem was introduced in commit a579f8a

dev kit: zig+llvm+lld+clang-x86_64-windows-gnu-0.7.0+1afea36a1

 C:\Users\Evan\Downloads\zig+llvm+lld+clang-x86_64-windows-gnu-0.7.0+1afea36a1\bin\zig.exe build -Dstage1 -Dtarget=native-native-gnu --search-prefix C:\Users\Evan\Downloads\zig+llvm+lld+clang-x86_64-windows-gnu-0.7.0+1afea36a1
.\src\link\MachO.zig:1819:34: error: container 'std.macho' has no member called 'EXPORT_SYMBOL_FLAGS_KIND_REGULAR'
            .export_flags = macho.EXPORT_SYMBOL_FLAGS_KIND_REGULAR,
                                 ^
.\src\link\MachO.zig:315:13: note: referenced here
            try self.writeExportTrie();
            ^
.\src\link.zig:479:13: note: referenced here
            try base.flushModule(comp);
            ^
.\src\Compilation.zig:1249:5: note: referenced here
    try self.bin_file.flush(self);
    ^
.\src\main.zig:1927:5: note: referenced here
    try comp.update();
    ^
.\src\main.zig:1789:49: note: referenced here
    updateModule(gpa, comp, zir_out_path, hook) catch |err| switch (err) {
                                                ^

[andrewrk]

ok so the unsolved problem with the dev kit is that every time we update the compiler in certain ways, you have to refresh the dev kit in order to keep it working. I have some ideas on how to improve this, but for now the solution is that I need to upload a new dev kit .zip file.

[andrewrk]

FYI the dev kit link is updated: https://github.com/ziglang/zig/wiki/Building-Zig-on-Windows

It solves this particular problem, but I'm going to keep the issue open to track the fact that we don't have a way to update the dev kit using the dev kit.

[ehaas]

One workaround for now is to additionally pass --override-lib-dir path\to\zig checkout\lib (e.g. --override-lib-dir C:\Users\Evan\projects\zig\lib) when using the compiler kit. This will work if trying to compile Zig when it uses new standard library features. It may not help if the compiler or build tools change in other ways though.

I confirmed that this workaround allows compiler kit 8076894d8 to build latest master 6ab5beb (without the additional flag it breaks due to missing std.fs.path.extension

[andrewrk]

I updated the wiki instructions to suggest the --override-lib-dir tip.