Unable to build the library using cargo lipo --release - ios

Question

Unable to build the library using cargo lipo --release
I am trying to make a cross-platform library using rust for ios target. I am following this article (Building and Deploying a Rust library on iOS).
*Note: I followed the same steps and my project structure also looks the same *
After completing the code and project setup the last step is to build the library. When I try to build the library using cargo lipo --release. It throws this error:
[ERROR cargo_lipo] No library target found for "my-project-name"
Also, note that I am only able to install support for two platforms. (aarch64-apple-ios and x86_64-apple-darwin). I think the reason is that they have dropped the support for 32-bit architectures.
So, when I run
rustup target add aarch64-apple-ios armv7-apple-ios armv7s-apple-ios x86_64-apple-ios i386-apple-ios.
It throws error: error: component 'rust-std' for target 'armv7-apple-ios' is unavailable for download for channel stable
Cargo.toml
[package]
name = "rustylib"
version = "0.1.0"
edition = "2018"
crate-type = ["staticlib", "cdylib"]
rustylib.rs
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
char *hello(const char *to);
void hello_release(char *s);
The rest of the project structure is the usual rust code.
The output of rustup show
Default host: x86_64-apple-darwin
rustup home: /Users/my-username/.rustup
installed toolchains
stable-x86_64-apple-darwin
nightly-x86_64-apple-darwin (default)
installed targets for active toolchain
aarch64-apple-ios
x86_64-apple-darwin
active toolchain
nightly-x86_64-apple-darwin (default)
rustc 1.52.0-nightly (acca81892 2021-03-13)
OS & Rust
Rust: rustc 1.50.0 (cb75ad5db 2021-02-10)
OS: macOS Bug Sur (11.2.3)
Xcode & Command line tools: 12.4

Answer 1

Your Cargo.toml is wrong.
If you look into the guide you linked in your question, you can see, that the crate-type has to be below the [lib] tag like so:
[package]
name = "greetings"
version = "0.1.1"
authors = ["fluffyemily <fluffyemily#mozilla.com>"]
description = "Example static library project built for iOS"
publish = false
[lib]
name = "greetings"
crate-type = ["staticlib", "cdylib"]
Also your code has to be in cargo/src/lib.rs by default as stated in the document (and not in rustylib.rs).
You can run cargo new rustylib --lib from the command line to create all the boilerplate, so that you only have to add the dependencies and the crate-type in the [lib] section of your Cargo.toml.
Edit
I think there is another problem:
You have entered C code in your rustylib.rs file, which can not work. I think what you intended to do, was to create the C bridge, which is called cargo/src/greetings.h in the guide you linked.