Rust noob: Sorry for being late here. What you can do is that you can include the bootloader as a blob by default in the app using something like: 
```
// Include the bootloader
#[cfg(feature = "bootloader")]
#[used]
#[link_section = ".bootloader"]
static BOOTLOADER: [u8; bootloader::BOOTLOADER_STM32F429_SIZE] = bootloader::BOOTLOADER_STM32F429;
```
You can define the bootloader section in memory.x.
Now when you have the bundled binary, then you can remove the bootloader section using `objcopy`