initfamfs: bring back to life. Was also easy!

build-linux

@@ -64,8 +64,6 @@ Run `make modules_install` after `make`.
 
     def build(self):
         build_dir = self.get_build_dir()
-        if self.env['initrd'] or self.env['initramfs']:
-            raise Exception('just trolling, --initrd and --initramfs are broken for now')
         os.makedirs(build_dir, exist_ok=True)
         tool = 'gcc'
         gcc = self.get_toolchain_tool(tool)
@@ -105,10 +103,12 @@ Run `make modules_install` after `make`.
             for i, config_fragment in enumerate(config_fragments):
                 config_fragments[i] = os.path.join(self.env['linux_config_dir'], config_fragment)
         config_fragments.extend(self.env['config_fragment'])
-        if self.env['config'] != []:
+        cli_configs = self.env['config']
+        if self.env['initramfs']:
+            cli_configs.append('CONFIG_INITRAMFS_SOURCE="{}"'.format(self.env['buildroot_cpio']))
+        if cli_configs:
             cli_config_fragment_path = os.path.join(build_dir, 'lkmc_cli_config_fragment')
-            cli_config_str = '\n'.join(self.env['config'])
-            self.sh.write_string_to_file(cli_config_fragment_path, cli_config_str)
+            self.sh.write_configs(cli_config_fragment_path, cli_configs, mode='w')
             config_fragments.append(cli_config_fragment_path)
         self.sh.cp(
             base_config_file,
@@ -136,6 +136,7 @@ Run `make modules_install` after `make`.
                     common_make_args +
                     self.sh.add_newlines(self.env['extra_make_args'])
                 ),
+                # https://github.com/cirosantilli/linux-kernel-module-cheat#proc-version
                 extra_env={
                     'KBUILD_BUILD_VERSION': '1',
                     'KBUILD_BUILD_TIMESTAMP': 'Thu Jan  1 00:00:00 UTC 1970',