Add musl aarch64 binaries (#295)

Or at least attempt to, let's see what PyPI says...

Author: alexcrichton

.github/workflows/main.yml

@@ -75,6 +75,9 @@ jobs:
     - run: |
         git clean -fdx wasmtime build
         python -m build --wheel -C=--build-option=--plat-name -C=--build-option=musllinux_1_2_x86_64
+    - run: |
+        git clean -fdx wasmtime build
+        python -m build --wheel -C=--build-option=--plat-name -C=--build-option=musllinux_1_2_aarch64
     - run: |
         git clean -fdx wasmtime build
         python -m build --wheel -C=--build-option=--plat-name -C=--build-option=android_26_x86_64

ci/_custom_build/backend.py

@@ -59,6 +59,7 @@ def plat_name_to_download_args(plat_name:str) -> list[str]:
         'manylinux1-x86_64':            ['linux', 'x86_64'],
         'manylinux2014_aarch64':        ['linux', 'aarch64'],
         'musllinux_1_2_x86_64':         ['musl', 'x86_64'],
+        'musllinux_1_2_aarch64':        ['musl', 'aarch64'],
         'win-amd64':                    ['win32', 'x86_64'],
         'win-arm64':                    ['win32', 'arm64'],
     }