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.

test/system/services/shared-memory-server/build.zig

@@ -0,0 +1,16 @@
+//! The shared-memory-server test fixture as a binary package (docs/build-packages-plan.md,
+//! phase 2): this file names only what is specific to this binary — the shared
+//! recipe and the default-import wiring live in build-support. The root build
+//! consumes the artifact(s) for the boot image.
+
+const std = @import("std");
+const build_support = @import("build-support");
+
+pub fn build(b: *std.Build) void {
+    const exe = build_support.userBinary(b, .{
+        .name = "shared-memory-server",
+        .root_source_file = b.path("shared-memory-server.zig"),
+        .domains = build_support.domains(b),
+    });
+    b.installArtifact(exe);
+}

test/system/services/shared-memory-server/build.zig.zon

@@ -0,0 +1,14 @@
+.{
+    .name = .shared_memory_server,
+    .version = "0.0.0",
+    .fingerprint = 0x5ebd8ca0f8a1675b, // 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" },
+    },
+    .paths = .{""},
+}