Failing to compile static binary on Raspberry PI3 - rust

Question

I am compiling my binary on a Raspberry device but when I move it to another one I get the following error:
./iot-relay
./iot-relay: error while loading shared libraries: libssl.so.1.1: cannot open shared object file: No such file or directory`
I've come to the conclusion that compiling a fully statically linked binary may help so I start reading about this here
Adding the target that I guess is appropriate:
rustup target add armv7-unknown-linux-musleabihf
And attempting to compile:
cargo build --release --target armv7-unknown-linux-musleabihf
It compiles most of the stuff but then:
error: failed to run custom build command for `paho-mqtt-sys v0.3.0`
Caused by:
process didn't exit successfully: `/home/pi/rust/iot-relay/target/release/build/paho-mqtt-sys-9d34dbf9179b933d/build-script-build` (exit code: 101)
--- stdout
debug:Running the bundled build for Paho C
cargo:rerun-if-changed=build.rs
running: "cmake" "/home/pi/.cargo/registry/src/github.com-1285ae84e5963aae/paho-mqtt-sys-0.3.0/paho.mqtt.c/" "-DPAHO_BUILD_SHARED=off" "-DPAHO_BUILD_STATIC=on" "-DPAHO_ENABLE_TESTING=off" "-DPAHO_WITH_SSL=on" "-DCMAKE_INSTALL_PREFIX=/home/pi/rust/iot-relay/target/armv7-unknown-linux-musleabihf/release/build/paho-mqtt-sys-964264b133c84ace/out" "-DCMAKE_C_FLAGS= -ffunction-sections -fdata-sections -fPIC -march=armv7-a" "-DCMAKE_C_COMPILER=arm-linux-musleabihf-gcc" "-DCMAKE_CXX_FLAGS= -ffunction-sections -fdata-sections -fPIC -march=armv7-a" "-DCMAKE_CXX_COMPILER=arm-linux-musleabihf-g++" "-DCMAKE_ASM_FLAGS= -ffunction-sections -fdata-sections -fPIC -march=armv7-a" "-DCMAKE_ASM_COMPILER=arm-linux-musleabihf-gcc" "-DCMAKE_BUILD_TYPE=Release"
-- The C compiler identification is unknown
-- Configuring incomplete, errors occurred!
See also "/home/pi/rust/iot-relay/target/armv7-unknown-linux-musleabihf/release/build/paho-mqtt-sys-964264b133c84ace/out/build/CMakeFiles/CMakeOutput.log".
See also "/home/pi/rust/iot-relay/target/armv7-unknown-linux-musleabihf/release/build/paho-mqtt-sys-964264b133c84ace/out/build/CMakeFiles/CMakeError.log".
--- stderr
fatal: not a git repository (or any of the parent directories): .git
CMake Error at CMakeLists.txt:21 (PROJECT):
The CMAKE_C_COMPILER:
arm-linux-musleabihf-gcc
is not a full path and was not found in the PATH.
Tell CMake where to find the compiler by setting either the environment
variable "CC" or the CMake cache entry CMAKE_C_COMPILER to the full path to
the compiler, or to the compiler name if it is in the PATH.
thread 'main' panicked at '
command did not execute successfully, got: exit code: 1
build script failed, must exit now', /home/pi/.cargo/registry/src/github.com-1285ae84e5963aae/cmake-0.1.44/src/lib.rs:885:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: build failed
How can I fix this and get my statically linked binary that would work on my other Raspberry? Unfortunately, the one that can't run the binary is a custom one and has some custom software that prevents me from doing system updates so I am hoping to pack everything required into the binary on the one over which I do have control.

Answer 1

This is cargo looking to follow build instructions to for a C dependency and not finding the gcc supporting the specified toolchain. You may need to find the correct location and name for your gcc targeting your environment (CC=). If you don't have a cross compiler for that target and musl libc combo, you may have to build one. See the link below for info on how to do that.
https://wiki.musl-libc.org/getting-started.html