WIP: move many global settings to become per-Module

Much of the logic from Compilation.create() is extracted into
Compilation.Config.resolve() which accepts many optional settings and
produces concrete settings. This separate step is needed by API users of
Compilation so that they can pass the resolved global settings to the
Module creation function, which itself needs to resolve per-Module
settings.

Since the target and other things are no longer global settings, I did
not want them stored in link.File (in the `options` field). That options
field was already a kludge; those options should be resolved into
concrete settings. This commit also starts to work on that, deleting
link.Options, moving the fields into Compilation and
ObjectFormat-specific structs instead. Some fields were ephemeral and
should not have been stored at all, such as symbol_size_hint.

The link.File object of Compilation is now a `?*link.File` and `null`
when -fno-emit-bin is passed. It is now arena-allocated along with
Compilation itself, avoiding some messy cleanup code that was there
before.

On the command line, it is now possible to configure the standard
library itself by using `--mod std` just like any other module. This
meant that the CLI needed to create the standard library module rather
than having Compilation create it.

There are a lot of changes in this commit and it's still not done. I
didn't realize how quickly this changeset was going to balloon out of
control, and there are still many lines that need to be changed before
it even compiles successfully.

* introduce std.Build.Cache.HashHelper.oneShot
* add error_tracing to std.Build.Module
* extract build.zig file generation into src/Builtin.zig
* each CSourceFile and RcSourceFile now has a Module owner, which
  determines some of the C compiler flags.

1 files changed, 3 insertions, 5 deletions

diff --git a/src/Module.zig b/src/Module.zig
index 6e5609f63c..5ec949293e 100644
--- a/src/Module.zig
+++ b/src/Module.zig
@@ -59,6 +59,7 @@ root_mod: *Package.Module,
 /// Normally, `main_mod` and `root_mod` are the same. The exception is `zig test`, in which
 /// `root_mod` is the test runner, and `main_mod` is the user's source file which has the tests.
 main_mod: *Package.Module,
+std_mod: *Package.Module,
 sema_prog_node: std.Progress.Node = undefined,
 
 /// Used by AstGen worker to load and store ZIR cache.
@@ -3599,7 +3600,7 @@ fn semaDecl(mod: *Module, decl_index: Decl.Index) !bool {
 
     // TODO: figure out how this works under incremental changes to builtin.zig!
     const builtin_type_target_index: InternPool.Index = blk: {
-        const std_mod = mod.main_mod.deps.get("std").?;
+        const std_mod = mod.std_mod;
         if (decl.getFileScope(mod).mod != std_mod) break :blk .none;
         // We're in the std module.
         const std_file = (try mod.importPkg(std_mod)).file;
@@ -3924,10 +3925,7 @@ pub fn importFile(
     import_string: []const u8,
 ) !ImportFileResult {
     if (std.mem.eql(u8, import_string, "std")) {
-        return mod.importPkg(mod.main_mod.deps.get("std").?);
-    }
-    if (std.mem.eql(u8, import_string, "builtin")) {
-        return mod.importPkg(mod.main_mod.deps.get("builtin").?);
+        return mod.importPkg(mod.std_mod);
     }
     if (std.mem.eql(u8, import_string, "root")) {
         return mod.importPkg(mod.root_mod);