don't build oniguruma when system integration is enabled (#4534)

follow-up to #4520

all the same stuff for the previous two

the tests for this only run for the native target and was added for the
iOS build (3360a00), I've made a second
version of this commit to remove the native check if thats more desired
(d247a22)

ghostty and all tests appear to run on my system both with and without
system integration

pkg/oniguruma/build.zig

@@ -5,36 +5,59 @@ pub fn build(b: *std.Build) !void {
     const target = b.standardTargetOptions(.{});
     const optimize = b.standardOptimizeOption(.{});
 
-    const module = b.addModule("oniguruma", .{ .root_source_file = b.path("main.zig") });
+    const module = b.addModule("oniguruma", .{
+        .root_source_file = b.path("main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
 
-    const upstream = b.dependency("oniguruma", .{});
-    const lib = try buildOniguruma(b, upstream, target, optimize);
-    module.addIncludePath(upstream.path("src"));
-    b.installArtifact(lib);
+    // 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()) {
-        const test_exe = b.addTest(.{
+        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 tests_run = b.addRunArtifact(test_exe.?);
         const test_step = b.step("test", "Run tests");
         test_step.dependOn(&tests_run.step);
 
         // Uncomment this if we're debugging tests
-        b.installArtifact(test_exe);
+        b.installArtifact(test_exe.?);
+    }
+
+    if (b.systemIntegrationOption("oniguruma", .{})) {
+        module.linkSystemLibrary("oniguruma", dynamic_link_opts);
+
+        if (test_exe) |exe| {
+            exe.linkSystemLibrary2("oniguruma", dynamic_link_opts);
+        }
+    } else {
+        const lib = try buildLib(b, module, .{
+            .target = target,
+            .optimize = optimize,
+        });
+
+        if (test_exe) |exe| {
+            exe.linkLibrary(lib);
+        }
     }
 }
 
-fn buildOniguruma(
-    b: *std.Build,
-    upstream: *std.Build.Dependency,
-    target: std.Build.ResolvedTarget,
-    optimize: std.builtin.OptimizeMode,
-) !*std.Build.Step.Compile {
+pub fn buildLib(b: *std.Build, module: *std.Build.Module, options: anytype) !*std.Build.Step.Compile {
+    const target = options.target;
+    const optimize = options.optimize;
+
+    const upstream = b.dependency("oniguruma", .{});
     const lib = b.addStaticLibrary(.{
         .name = "oniguruma",
         .target = target,
@@ -43,6 +66,7 @@ fn buildOniguruma(
     const t = target.result;
     lib.linkLibC();
     lib.addIncludePath(upstream.path("src"));
+    module.addIncludePath(upstream.path("src"));
 
     if (target.result.isDarwin()) {
         const apple_sdk = @import("apple_sdk");
@@ -134,5 +158,7 @@ fn buildOniguruma(
         .{ .include_extensions = &.{".h"} },
     );
 
+    b.installArtifact(lib);
+
     return lib;
 }