Fix for --preload-file + --embed-file (#17457)

Without this the embedded file is loaded twice (once via JS and once
via the object file) causing a runtime error.

I noticed this while working on the interactive tests, one of which
actually does this.

Author: sbc100

tests/test_other.py

@@ -1554,11 +1554,13 @@ def test_export_from_archive(self):
 
   @parameterized({
     'embed': (['--embed-file', 'somefile.txt'],),
-    'embed-twice': (['--embed-file', 'somefile.txt', '--embed-file', 'somefile.txt'],),
-    'preload': (['--preload-file', 'somefile.txt'],)
+    'embed_twice': (['--embed-file', 'somefile.txt', '--embed-file', 'somefile.txt'],),
+    'preload': (['--preload-file', 'somefile.txt'],),
+    'preload_and_embed': (['--preload-file', 'somefile.txt', '--embed-file', 'hello.txt'],)
   })
   def test_include_file(self, args):
     create_file('somefile.txt', 'hello from a file with lots of data and stuff in it thank you very much')
+    create_file('hello.txt', 'hello world')
     create_file('main.c', r'''
       #include <assert.h>
       #include <stdio.h>

tools/file_packager.py

@@ -682,12 +682,13 @@ def generate_js(data_target, data_files, metadata):
     dirname = os.path.dirname(filename)
     basename = os.path.basename(filename)
     if file_.mode == 'embed':
-      # Embed
-      data = base64_encode(utils.read_binary(file_.srcpath))
-      code += "      var fileData%d = '%s';\n" % (counter, data)
-      # canOwn this data in the filesystem (i.e. there is no need to create a copy in the FS layer).
-      code += ("      Module['FS_createDataFile']('%s', '%s', decodeBase64(fileData%d), true, true, true);\n"
-               % (dirname, basename, counter))
+      if not options.obj_output:
+        # Embed (only needed when not generating object file output)
+        data = base64_encode(utils.read_binary(file_.srcpath))
+        code += "      var fileData%d = '%s';\n" % (counter, data)
+        # canOwn this data in the filesystem (i.e. there is no need to create a copy in the FS layer).
+        code += ("      Module['FS_createDataFile']('%s', '%s', decodeBase64(fileData%d), true, true, true);\n"
+                 % (dirname, basename, counter))
     elif file_.mode == 'preload':
       # Preload
       metadata_el = {