[Breaking] Support multiple src files and compile steps as emcc input

Author: hazeycode

README.md

@@ -39,7 +39,8 @@ Add zemscripten's "root" module to your wasm compile target., then create an `em
 
     const emcc_step = @import("zemscripten").emccStep(
         b,
-        .{ .compile_step = wasm },
+        &.{ }, // src file paths 
+        &.{ wasm }, // src compile steps
         .{
             .optimize = optimize,
             .flags = emcc_flags,
@@ -49,31 +50,14 @@ Add zemscripten's "root" module to your wasm compile target., then create an `em
             .preload_paths = &.{},
             .out_file_name = null, // emcc output arg will default to {wasm.name}.html if unset
             .install_dir = .{ .custom = "web" },
+            .shell_file_path = null, // set this to override the default html shell
         },
     );
     emcc_step.dependOn(activate_emsdk_step);
 
     b.getInstallStep().dependOn(emcc_step);
 ```
 
-To use a custom html file emccStep() accepts a shell_file_path option:
-```zig
-    const emcc_step = @import("zemscripten").emccStep(
-        b,
-        wasm,
-        .{
-            .optimize = optimize,
-            .flags = emcc_flags,
-            .settings = emcc_settings,
-            .use_preload_plugins = true,
-            .embed_paths = &.{},
-            .preload_paths = &.{},
-            .install_dir = .{ .custom = "web" },
-            .shell_file_path = b.path("path/to/file"),
-        },
-    );
-```
-
 Now you can use the provided Zig panic and log overrides in your wasm's root module and define the entry point that invoked by the js output of `emcc` (by default it looks for a symbol named `main`). For example:
 ```zig
 const std = @import("std");

build.zig

@@ -187,10 +187,8 @@ pub const StepOptions = struct {
 
 pub fn emccStep(
     b: *std.Build,
-    src_path_or_compile_step: union(enum) {
-        src_path: std.Build.LazyPath,
-        compile_step: *std.Build.Step.Compile,
-    },
+    src_paths: []const []const u8,
+    compile_steps: []const *std.Build.Step.Compile,
     options: StepOptions,
 ) *std.Build.Step {
     var emcc = b.addSystemCommand(&.{emccPath(b)});
@@ -209,28 +207,27 @@ pub fn emccStep(
         ) catch unreachable);
     }
 
-    switch (src_path_or_compile_step) {
-        .src_path => |src_path| {
-            emcc.addArg(src_path.getPath(b));
-        },
-        .compile_step => |compile_step| {
-            emcc.addArtifactArg(compile_step);
-            for (compile_step.root_module.getGraph().modules) |module| {
-                for (module.link_objects.items) |link_object| {
-                    switch (link_object) {
-                        .other_step => |linked_compile_step| {
-                            switch (linked_compile_step.kind) {
-                                .lib => {
-                                    emcc.addArtifactArg(linked_compile_step);
-                                },
-                                else => {},
-                            }
-                        },
-                        else => {},
-                    }
+    for (src_paths) |src_path| {
+        emcc.addArg(src_path);
+    }
+
+    for (compile_steps) |compile_step| {
+        emcc.addArtifactArg(compile_step);
+        for (compile_step.root_module.getGraph().modules) |module| {
+            for (module.link_objects.items) |link_object| {
+                switch (link_object) {
+                    .other_step => |linked_compile_step| {
+                        switch (linked_compile_step.kind) {
+                            .lib => {
+                                emcc.addArtifactArg(linked_compile_step);
+                            },
+                            else => {},
+                        }
+                    },
+                    else => {},
                 }
             }
-        },
+        }
     }
 
     emcc.addArg("-o");