build: phase 2 wave A — services build as packages

init, fat, display, display-demo, device-manager, input, logger, and
the two discovery fillers (acpi, fdt — each exporting an artifact named
"discovery"; the root -Ddiscovery picks which ships) convert to binary
packages on the pci-bus template. init's serial heartbeat flag rides
the dependency options (the root forwards its -Dserial). fat's and
display's unit tests move into their packages and the root aggregate
delegates to them. Boot-image file list unchanged.

system/services/acpi/build.zig

@@ -0,0 +1,24 @@
+//! The acpi discovery service as a binary package (docs/build-packages-plan.md,
+//! phase 2). The artifact is named "discovery": one swappable process per
+//! firmware fills the ramdisk's neutral `discovery` slot (docs/discovery.md),
+//! so the device manager never learns which firmware it is on. The root
+//! build's -Ddiscovery picks this package or `fdt`.
+
+const std = @import("std");
+const build_support = @import("build-support");
+
+pub fn build(b: *std.Build) void {
+    const exe = build_support.userBinary(b, .{
+        .name = "discovery",
+        .root_source_file = b.path("acpi.zig"),
+        .domains = build_support.domains(b),
+    });
+    const protocol = b.dependency("protocol", .{});
+    // The shared AML interpreter (the same parser the kernel runs), the
+    // device-manager report channel, and the power protocol (the SCI/power
+    // button path, docs/power.md).
+    build_support.programModule(exe).addImport("aml", b.dependency("device", .{}).module("aml"));
+    build_support.programModule(exe).addImport("device-manager-protocol", protocol.module("device-manager-protocol"));
+    build_support.programModule(exe).addImport("power-protocol", protocol.module("power-protocol"));
+    b.installArtifact(exe);
+}

system/services/acpi/build.zig.zon

@@ -0,0 +1,15 @@
+.{
+    .name = .acpi,
+    .version = "0.0.0",
+    .fingerprint = 0xf31e9a0903256b64, // Changing this has security and trust implications.
+    .minimum_zig_version = "0.16.0",
+    .dependencies = .{
+        .@"build-support" = .{ .path = "../../../build-support" },
+        .kernel = .{ .path = "../../../library/kernel" },
+        .device = .{ .path = "../../../library/device" },
+        .client = .{ .path = "../../../library/client" },
+        .@"xkeyboard-config" = .{ .path = "../../../library/xkeyboard-config" },
+        .protocol = .{ .path = "../../../library/protocol" },
+    },
+    .paths = .{""},
+}