selfhost: List dependencies of main output file in generated depfile

selfhost/main.jakt

@@ -452,6 +452,11 @@ fn find_with_extension(path: Path, extension: String) throws -> [Path] {
     return files_found
 }
 
+fn escape_for_depfile(anon input: String) throws -> String {
+    // $ -> $$, # -> \#, <space> -> \<space>
+    return input.replace(replace: "$", with: "$$").replace(replace: "#", with: "\\#").replace(replace: " ", with: "\\ ")
+}
+
 fn compiler_main(anon args: [String]) throws -> c_int {
     mut args_parser = ArgsParser::from_args(args)
 
@@ -873,6 +878,21 @@ fn compiler_main(anon args: [String]) throws -> c_int {
 
     mut depfile_builder = StringBuilder::create()
 
+    if generate_depfile.has_value() {
+        if link_archive.has_value() {
+            depfile_builder.append(escape_for_depfile(binary_dir.join(link_archive!).to_string()))
+        } else {
+            depfile_builder.append(escape_for_depfile(output_filename))
+        }
+        depfile_builder.append(" : ")
+        for (file, _) in codegen_result {
+            let path = binary_dir.join(file)
+            depfile_builder.append(" \\\n  ")
+            depfile_builder.append(escape_for_depfile(path.to_string()))
+        }
+        depfile_builder.append("\n")
+    }
+
     if not binary_dir.exists() {
         make_directory(path: binary_dir.to_string())
     }
@@ -886,13 +906,14 @@ fn compiler_main(anon args: [String]) throws -> c_int {
             return 1
         }
 
-        if generate_depfile.has_value() and file.ends_with(".cpp") {
-            let escaped = file.replace(replace: " ", with: "\\ ")
-            let escaped_module_file_path = module_file_path.replace(replace: " ", with: "\\ ")
+        if generate_depfile.has_value() and file.ends_with(".cpp") and module_file_path != "__prelude__" {
+            let f = binary_dir.join(file).to_string()
+            let escaped = escape_for_depfile(f)
+            let escaped_module_file_path = escape_for_depfile(module_file_path)
             depfile_builder.append_string(format(
                 "{} {}.h: {}"
                 escaped
-                escaped.substring(start: 0, length: file.length() - 4)
+                escaped.substring(start: 0, length: escaped.length() - 4)
                 escaped_module_file_path
             ))
             depfile_builder.append(b'\n')