gpu: decouple SDK from dependencies

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

gpu/sdk.zig

@@ -0,0 +1,40 @@
+const std = @import("std");
+// const gpu_dawn = @import("libs/mach-gpu-dawn/build.zig");
+// const glfw = @import("libs/mach-glfw/build.zig");
+
+pub fn Sdk(deps: anytype) type {
+    return struct {
+        pub fn testStep(b: *std.build.Builder, mode: std.builtin.Mode, target: std.zig.CrossTarget, options: Options) *std.build.RunStep {
+            const main_tests = b.addTestExe("gpu-tests", (comptime thisDir()) ++ "/src/main.zig");
+            main_tests.setBuildMode(mode);
+            main_tests.setTarget(target);
+            link(b, main_tests, options);
+            main_tests.install();
+            return main_tests.run();
+        }
+
+        pub const Options = struct {
+            glfw_options: deps.glfw.Options = .{},
+            gpu_dawn_options: deps.gpu_dawn.Options = .{},
+        };
+
+        pub const pkg = std.build.Pkg{
+            .name = "gpu",
+            .source = .{ .path = thisDir() ++ "/src/main.zig" },
+            .dependencies = &.{deps.glfw.pkg},
+        };
+
+        pub fn link(b: *std.build.Builder, step: *std.build.LibExeObjStep, options: Options) void {
+            if (step.target.toTarget().cpu.arch != .wasm32) {
+                deps.glfw.link(b, step, options.glfw_options);
+                deps.gpu_dawn.link(b, step, options.gpu_dawn_options);
+                step.addCSourceFile((comptime thisDir()) ++ "/src/mach_dawn.cpp", &.{"-std=c++17"});
+                step.addIncludeDir((comptime thisDir()) ++ "/src");
+            }
+        }
+
+        fn thisDir() []const u8 {
+            return std.fs.path.dirname(@src().file) orelse ".";
+        }
+    };
+}