Add Emscripten sysroot include paths to enable C library compilation …

README.md

@@ -27,6 +27,39 @@ pub fn build(b: *std.Build) void {
 }
 ```
 
+Zemscripten `build.zig` example:
+```zig
+pub fn build(b: *std.Build) void {
+    const target = b.resolveTargetQuery(.{
+        .cpu_arch = .wasm32,
+        .os_tag = .emscripten,
+    });
+
+    const wasm = b.addLibrary(.{ .name = "zemscripten-build", .linkage = .static, .root_module = b.createModule(.{
+        .root_source_file = b.path("main.zig"),
+        .target = target,
+        .optimize = optimize,
+    }) });
+
+    // Add Emscripten include paths for @cImport
+    const emsdk_path = b.dependency("emsdk", .{}).path("").getPath(b);
+    const emscripten_include_path = b.pathJoin(&.{ emsdk_path, "upstream", "emscripten", "cache", "sysroot", "include" });
+    wasm.root_module.addSystemIncludePath(.{ .cwd_relative = emscripten_include_path });
+
+    const zemscripten = b.dependency("zemscripten", .{});
+    const zmesh = b.dependency("zmesh", .{
+        .target = target,
+        .optimize = optimize,
+        .emscripten_include_path = emscripten_include_path,
+    });
+
+    wasm.root_module.addImport("zmesh", zmesh.module("root"));
+    wasm.linkLibrary(zmesh.artifact("zmesh"));
+
+    ...
+}
+```
+
 Now in your code you may import and use `zmesh`:
 
 ```zig

build.zig

@@ -15,6 +15,11 @@ pub fn build(b: *std.Build) void {
             "shared",
             "Build as shared library",
         ) orelse false,
+        .emscripten_include_path = b.option(
+            []const u8,
+            "emscripten_include_path",
+            "Path to emscripten include directory for Emscripten builds",
+        ),
     };
 
     const options_step = b.addOptions();
@@ -54,6 +59,15 @@ pub fn build(b: *std.Build) void {
     if (target.result.abi != .msvc)
         zmesh_lib.linkLibCpp();
 
+    // Add Emscripten sysroot include paths when building for emscripten target
+    if (target.result.os.tag == .emscripten) {
+        if (options.emscripten_include_path) |emscripten_include_path| {
+            zmesh_lib.addSystemIncludePath(.{ .cwd_relative = emscripten_include_path });
+        } else {
+            std.debug.panic("emscripten_include_path option must be provided when building for emscripten target\n", .{});
+        }
+    }
+
     const par_shapes_t = if (options.shape_use_32bit_indices)
         "-DPAR_SHAPES_T=uint32_t"
     else