Compiler 'aarch64-linux-gnu-gcc' not found

Change to the directory where the source code was extracted:

Installing the GCC compiler on an Arch-based Linux system is a straightforward process.
You can run the following Pacman command given below on the terminal shell of your Arch Linux system to install the GNU Compiler Collection.

To compile aarch64 versions of all the executables, you must simply run the following command at the root of the library:

aarch64-linux-gnu-gcc is a Linux x86_64 binary, so it will run only on a Linux machine running a 64-bit distribution for Intel-compatible CPUs.
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I don't really get it, this means they say it should work on Raspberry but because the processor is actually an ARM it won't work on it ? .

Currently it only supports the aarch64 platform

It is specifically designed for linux kernels that enable the CONFIG_SHADOW_CALL_STACK option

For the user space programs, runtime support is not currently provided in libc and libgcc

If you only want some of the stages of compilation, you can use -x(or filename suffixes) to tell gccwhere to start, and one of the options -c, -S, or -Eto say where gccis to stop

Note that some combinations (for example, -x cpp-output -E) instruct gccto do nothing at all

-c Compile or assemble the source files, but do not link

Package gcc-aarch64-linux-gnu is not available, but is referred to by another package

This may mean that the package is missing, has been obsoleted, or is only available from another source Package g++-aarch64-linux-gnu is not available, but is referred to by another package