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### Issue Details

* **Electron Version:**
  * 9.3.4
* **Operating System:**
  * Arch Linux
* **Last Known Working Electron version:**
  * 9.3.3

### Expected Behavior
```
❱ echo lang: $LANG lc_all: $LC_ALL
lang: en_US.UTF-8 lc_all:
❱ electron9 -i                    
> process.env.LC_ALL
undefined
```

### Actual Behavior
```
❱ echo lang: $LANG lc_all: $LC_ALL
lang: en_US.UTF-8 lc_all:
❱ electron9 -i                    
> process.env.LC_ALL
'en_US'
```

`en_US` is not a valid locale—it has to be `en_US.UTF-8`, however, Electron overrides this, even if `--lang=en_US.UTF-8` is passed or `LC_ALL` is set correctly when invoking Electron. With this invalid value, many C programs fail to run.

### To Reproduce
Run the above commands.

### Additional Information
Problem introduced in  #26242
shell/browser/electron_browser_main_parts.cc
#include "content/public/browser/device_service.h"
#include "content/public/browser/web_ui_controller_factory.h"
#include "content/public/common/content_features.h"
#include "content/public/common/content_switches.h"
#include "content/public/common/result_codes.h"
#include "electron/buildflags/buildflags.h"
#include "media/base/localized_strings.h"
#include "services/network/public/cpp/features.h"
#include "services/tracing/public/cpp/stack_sampling/tracing_sampler_profiler.h"
#include "shell/app/electron_main_delegate.h"
#include "shell/browser/api/electron_api_app.h"
#include "shell/browser/browser.h"
#include "shell/browser/browser_process_impl.h"
#include "shell/browser/electron_browser_client.h"
#include "shell/browser/electron_browser_context.h"
#include "shell/browser/electron_web_ui_controller_factory.h"
#include "shell/browser/feature_list.h"
#include "shell/browser/javascript_environment.h"
#include "shell/browser/media/media_capture_devices_dispatcher.h"
#include "shell/browser/ui/devtools_manager_delegate.h"
#include "shell/common/api/electron_bindings.h"
#include "shell/common/application_info.h"
#include "shell/common/asar/asar_util.h"
#include "shell/common/electron_paths.h"
#include "shell/common/gin_helper/trackable_object.h"
#include "shell/common/node_bindings.h"
#include "shell/common/node_includes.h"
#include "ui/base/idle/idle.h"
#include "ui/base/l10n/l10n_util.h"
#include "ui/base/ui_base_switches.h"