fix version number (#6)

Author: zivoy

build.zig

@@ -1,12 +1,15 @@
 const std = @import("std");
 
-const version: std.SemanticVersion = .{ .major = 2, .minor = 13, .patch = 5 };
-
 pub fn build(b: *std.Build) void {
     const upstream = b.dependency("libxml2", .{});
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
+    // get version from zon file
+    const versionString = @import("./build.zig.zon").version;
+    const version = std.SemanticVersion.parse(versionString) catch @panic("OOM");
+    const versionNumber = version.major * 1_00_00 + version.minor * 1_00 + version.patch;
+
     const linkage = b.option(std.builtin.LinkMode, "linkage", "Link mode") orelse .static;
     const strip = b.option(bool, "strip", "Omit debug information");
     const pic = b.option(bool, "pie", "Produce Position Independent Code");
@@ -84,8 +87,8 @@ pub fn build(b: *std.Build) void {
         .include_path = "libxml/xmlversion.h",
         .style = .{ .cmake = upstream.path("include/libxml/xmlversion.h.in") },
     }, .{
-        .VERSION = b.fmt("{f}", .{version}),
-        .LIBXML_VERSION_NUMBER = @as(i64, version.major * 10000 + version.major * 100 + version.patch),
+        .VERSION = b.fmt("{f}", .{std.SemanticVersion{ .major = version.major, .minor = version.minor, .patch = version.patch }}),
+        .LIBXML_VERSION_NUMBER = @as(i64, @intCast(versionNumber)),
         .LIBXML_VERSION_EXTRA = "",
         .WITH_THREADS = threads,
         .WITH_THREAD_ALLOC = thread_alloc,