don't build freetype2 when system integration is enabled (#4543)

yet another follow up to #4534

some notes:
- different parts of the build system link against freetype2 or freetype
with freetype2 being the name for the pkg-config file. Because of the
include path in freetype-zig.h the pkg-config is needed otherwise it
would be unable to find the headers. The change isn't technically needed
for the harfbuzz and fontconfig modules however I think its best to keep
them all consistent since otherwise it might cause build errors in non
standard setups
- looking back, I initially modelled buildLib after the build function
and kept the pub, none of them need to be public so I've gone ahead and
removed all of that

test logic was kept just as they were before with a setup exact like it
was done for oniguruma

the main program and the testsall seem to work just fine both with and
without system integration

pkg/fontconfig/build.zig

@@ -56,7 +56,7 @@ pub fn build(b: *std.Build) !void {
     }
 }
 
-pub fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
+fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
     const target = options.target;
     const optimize = options.optimize;
 
@@ -186,7 +186,7 @@ pub fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*st
     _ = b.systemIntegrationOption("freetype", .{}); // So it shows up in help
     if (freetype_enabled) {
         if (b.systemIntegrationOption("freetype", .{})) {
-            lib.linkSystemLibrary2("freetype", dynamic_link_opts);
+            lib.linkSystemLibrary2("freetype2", dynamic_link_opts);
         } else {
             const freetype_dep = b.dependency(
                 "freetype",

pkg/freetype/build.zig

@@ -5,7 +5,61 @@ pub fn build(b: *std.Build) !void {
     const optimize = b.standardOptimizeOption(.{});
     const libpng_enabled = b.option(bool, "enable-libpng", "Build libpng") orelse false;
 
-    const module = b.addModule("freetype", .{ .root_source_file = b.path("main.zig") });
+    const module = b.addModule("freetype", .{
+        .root_source_file = b.path("main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // For dynamic linking, we prefer dynamic linking and to search by
+    // mode first. Mode first will search all paths for a dynamic library
+    // before falling back to static.
+    const dynamic_link_opts: std.Build.Module.LinkSystemLibraryOptions = .{
+        .preferred_link_mode = .dynamic,
+        .search_strategy = .mode_first,
+    };
+
+    var test_exe: ?*std.Build.Step.Compile = null;
+    if (target.query.isNative()) {
+        test_exe = b.addTest(.{
+            .name = "test",
+            .root_source_file = b.path("main.zig"),
+            .target = target,
+            .optimize = optimize,
+        });
+        const tests_run = b.addRunArtifact(test_exe.?);
+        const test_step = b.step("test", "Run tests");
+        test_step.dependOn(&tests_run.step);
+    }
+
+    module.addIncludePath(b.path(""));
+
+    if (b.systemIntegrationOption("freetype", .{})) {
+        module.linkSystemLibrary("freetype2", dynamic_link_opts);
+        if (test_exe) |exe| {
+            exe.linkSystemLibrary2("freetype2", dynamic_link_opts);
+        }
+    } else {
+        const lib = try buildLib(b, module, .{
+            .target = target,
+            .optimize = optimize,
+
+            .libpng_enabled = libpng_enabled,
+
+            .dynamic_link_opts = dynamic_link_opts,
+        });
+
+        if (test_exe) |exe| {
+            exe.linkLibrary(lib);
+        }
+    }
+}
+
+fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
+    const target = options.target;
+    const optimize = options.optimize;
+
+    const libpng_enabled = options.libpng_enabled;
 
     const upstream = b.dependency("freetype", .{});
     const lib = b.addStaticLibrary(.{
@@ -21,16 +75,6 @@ pub fn build(b: *std.Build) !void {
     }
 
     module.addIncludePath(upstream.path("include"));
-    module.addIncludePath(b.path(""));
-
-    // For dynamic linking, we prefer dynamic linking and to search by
-    // mode first. Mode first will search all paths for a dynamic library
-    // before falling back to static.
-    const dynamic_link_opts: std.Build.Module.LinkSystemLibraryOptions = .{
-        .preferred_link_mode = .dynamic,
-        .search_strategy = .mode_first,
-    };
-
     var flags = std.ArrayList([]const u8).init(b.allocator);
     defer flags.deinit();
     try flags.appendSlice(&.{
@@ -44,6 +88,8 @@ pub fn build(b: *std.Build) !void {
         "-fno-sanitize=undefined",
     });
 
+    const dynamic_link_opts = options.dynamic_link_opts;
+
     // Zlib
     if (b.systemIntegrationOption("zlib", .{})) {
         lib.linkSystemLibrary2("zlib", dynamic_link_opts);
@@ -113,18 +159,7 @@ pub fn build(b: *std.Build) !void {
 
     b.installArtifact(lib);
 
-    if (target.query.isNative()) {
-        const test_exe = b.addTest(.{
-            .name = "test",
-            .root_source_file = b.path("main.zig"),
-            .target = target,
-            .optimize = optimize,
-        });
-        test_exe.linkLibrary(lib);
-        const tests_run = b.addRunArtifact(test_exe);
-        const test_step = b.step("test", "Run tests");
-        test_step.dependOn(&tests_run.step);
-    }
+    return lib;
 }
 
 const srcs: []const []const u8 = &.{

pkg/harfbuzz/build.zig

@@ -43,7 +43,11 @@ pub fn build(b: *std.Build) !void {
     {
         var it = module.import_table.iterator();
         while (it.next()) |entry| test_exe.root_module.addImport(entry.key_ptr.*, entry.value_ptr.*);
-        test_exe.linkLibrary(freetype.artifact("freetype"));
+        if (b.systemIntegrationOption("freetype", .{})) {
+            test_exe.linkSystemLibrary2("freetype2", dynamic_link_opts);
+        } else {
+            test_exe.linkLibrary(freetype.artifact("freetype"));
+        }
         const tests_run = b.addRunArtifact(test_exe);
         const test_step = b.step("test", "Run tests");
         test_step.dependOn(&tests_run.step);
@@ -67,7 +71,7 @@ pub fn build(b: *std.Build) !void {
     }
 }
 
-pub fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
+fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
     const target = options.target;
     const optimize = options.optimize;
 

pkg/oniguruma/build.zig

@@ -53,7 +53,7 @@ pub fn build(b: *std.Build) !void {
     }
 }
 
-pub fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
+fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
     const target = options.target;
     const optimize = options.optimize;