add a minimal build file to compile st with zig

this ignores config.h, tic -sx st.info and man page gen for now.

build.zig

@@ -0,0 +1,26 @@
+const std = @import("std");
+
+pub fn build(b: *std.build.Builder) void {
+    const target = b.standardTargetOptions(.{});
+    const mode = b.standardReleaseOptions();
+
+    const exe = b.addExecutable("st", null);
+    exe.setTarget(target);
+    exe.setBuildMode(mode);
+    exe.install();
+    exe.linkSystemLibrary("fontconfig");
+    exe.linkSystemLibrary("freetype2");
+    exe.linkSystemLibrary("Xft");
+    exe.linkSystemLibrary("X11");
+    exe.linkLibC();
+    exe.pie = true;
+    exe.addCSourceFiles(&.{
+        "st.c",
+        "x.c",
+    }, &.{
+        "-DVERSION=\"0.8.4.1\"",
+        "-D_XOPEN_SOURCE=600",
+        "-Wall",
+        "-Werror",
+    });
+}