cargo builder can't detect bootloader when it is declared as a target-dependent dependency

[PatchMixolydic]

While trying to migrate an old project to bootloader 0.10, I ran the following command:

<cargo registry>/bootloader-0.10.6 $ cargo builder --kernel-manifest <correct path>/Cargo.toml --kernel-binary <correct path>/target/x86_64-unknown-spinel_kernel/debug/spinel

which resulted in this error:

   Compiling bootloader v0.10.6 (/home/patchmixolydic/.cargo/registry/src/github.com-1ecc6299db9ec823/bootloader-0.10.6)
error: no bootloader dependency in /home/patchmixolydic/Programming/Rust/Spinel/Cargo.toml

  The `--kernel-manifest` path should point to the `Cargo.toml` of the kernel.
 --> /home/patchmixolydic/.cargo/registry/src/github.com-1ecc6299db9ec823/bootloader-0.10.6/target/x86_64-unknown-uefi/release/build/bootloader-b9ead764961ec1c9/out/bootloader_config.rs:1:81
  |
1 | ... = compile_error ! ("no bootloader dependency in /home/patchmixolydic/Programming/Rust/Spinel/Cargo.toml\n\n  The `--kernel-manifest` path should point to the `Cargo.toml` of the kernel.") ...
  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is strange since my kernel does have a bootloader dependency. The source of this error is this check, which looks for the dependency in the [dependencies] section:

bootloader/build.rs

Lines 243 to 246 in c09f94f

	if manifest
	.get("dependencies")
	.and_then(|d| d.get("bootloader"))
	.is_some()

Normally this would work, but this misses the case where bootloader is a target-dependent dependency. Indeed, that's exactly what my project's Cargo.toml does:

[target.'cfg(target_arch = "x86_64")'.dependencies]
bootloader = "0.10.6"
x86_64 = "0.14.4"

Ideally, this would be supported to allow for multi-platform kernels.

[yusdacra]

I also faced this issue before (see #181), #182 fixes it for me.

[PatchMixolydic]

My mistake 😅
Closing as a duplicate of #181