Fix linking of tool on Linux AArch64

I specified the linker to `aarch64-none-elf-ld` because I would've
thought that even though we are targeting Linux, the linker shouldn't
matter but on Linux AArch64 we get a segfault when running the Microkit
tool.

Changing the linker to `aarch64-linux-gnu-ld` fixes that.

I'm not really happy with this solution as we now have to install a new
C toolchain just to compile a Rust program, from searching on the
internet the solution seems to be to use the cross-rs package, which
just uses Docker containers so isn't actually cross compiling anything.

If anyone has any better ideas please let me know.

Signed-off-by: Ivan Velickovic <[email protected]>

.github/workflows/sdk.yaml

@@ -45,7 +45,8 @@ jobs:
             texlive-fonts-recommended texlive-fonts-extra \
             libxml2-utils \
             python3.9 python3-pip python3.9-venv \
-            qemu-system-arm qemu-system-misc
+            qemu-system-arm qemu-system-misc \
+            gcc-aarch64-linux-gnu
           python3.9 -m venv pyenv
           ./pyenv/bin/pip install --upgrade pip setuptools wheel
           ./pyenv/bin/pip install -r requirements.txt

tool/microkit/.cargo/config.toml

@@ -2,4 +2,4 @@
 # SPDX-License-Identifier: BSD-2-Clause
 
 [target.aarch64-unknown-linux-musl]
-linker = "aarch64-none-elf-ld"
+linker = "aarch64-linux-gnu-ld"