feat: Add arm64/aarch64 support to fd package

The `fd` releases have amd64 and arm64 binaries (using the xarch
architecture tag). Change the hardcoded `x86_64` to `${xarch}` so we can
get appropriate binaries on arm64.

The following are the related assets in the lastest v10.2.0 release:

    fd-v10.2.0-aarch64-apple-darwin.tar.gz
    fd-v10.2.0-aarch64-unknown-linux-musl.tar.gz
    fd-v10.2.0-x86_64-apple-darwin.tar.gz
    fd-v10.2.0-x86_64-unknown-linux-musl.tar.gz

fd.hcl

@@ -4,11 +4,11 @@ strip = 1
 test = "fd --version"
 
 platform "linux" {
-  source = "https://github.com/sharkdp/fd/releases/download/v${version}/fd-v${version}-x86_64-unknown-linux-musl.tar.gz"
+  source = "https://github.com/sharkdp/fd/releases/download/v${version}/fd-v${version}-${xarch}-unknown-linux-musl.tar.gz"
 }
 
 platform "darwin" {
-  source = "https://github.com/sharkdp/fd/releases/download/v${version}/fd-v${version}-x86_64-apple-darwin.tar.gz"
+  source = "https://github.com/sharkdp/fd/releases/download/v${version}/fd-v${version}-${xarch}-apple-darwin.tar.gz"
 }
 
 version "8.3.2" "8.6.0" "8.7.0" "8.7.1" "9.0.0" "10.0.0" "10.1.0" "10.2.0" {