add main engine library + minimal glfw linking example

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

build.zig

@@ -0,0 +1,19 @@
+const Builder = @import("std").build.Builder;
+const glfw = @import("glfw/build.zig");
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+    const lib = b.addStaticLibrary("engine", "src/main.zig");
+    lib.addPackagePath("glfw", "glfw/src/main.zig");
+    lib.setBuildMode(mode);
+    glfw.link(b, lib, .{});
+    lib.install();
+
+    var main_tests = b.addTest("src/main.zig");
+    main_tests.addPackagePath("glfw", "glfw/src/main.zig");
+    glfw.link(b, main_tests, .{});
+    main_tests.setBuildMode(mode);
+
+    const test_step = b.step("test", "Run library tests");
+    test_step.dependOn(&main_tests.step);
+}

src/main.zig

@@ -0,0 +1,8 @@
+const std = @import("std");
+const testing = std.testing;
+
+const glfw = @import("glfw");
+
+test "glfw_basic" {
+    glfw.basicTest();
+}