fix(ci): Revert runtime to musl (#3278)

Turns out #3276 was only part of the problem. After that was fixed, the
issue did turn out to be the statically-linked libc runtime. Staging was
using dynamic linking and so didn't hit the issue.

This reverts back to musl which has been tested as @AndrewDryga noted.

.github/workflows/cd.yml

@@ -113,17 +113,17 @@ jobs:
       fail-fast: false
       matrix:
         arch:
-          - target: x86_64-unknown-linux-gnu
+          - target: x86_64-unknown-linux-musl
             shortname: x64
             platform: linux/amd64
-          - target: aarch64-unknown-linux-gnu # E.g. AWS Graviton
+          - target: aarch64-unknown-linux-musl # E.g. AWS Graviton
             shortname: arm64
             platform: linux/arm64
-          - target: armv7-unknown-linux-gnueabihf # E.g. Raspberry Pi
+          - target: armv7-unknown-linux-musleabihf # E.g. Raspberry Pi
             platform: linux/arm/v7
             shortname: arm
           # Requires ring v0.17 which a number of our dependencies don't yet support
-          # - target: mips64-unknown-linux-gnuabi64 # E.g. UniFi Routers
+          # - target: mips64-unknown-linux-muslabi64 # E.g. UniFi Routers
           #   platform: linux/mips64le
         name:
           - package: firezone-linux-client
@@ -141,14 +141,11 @@ jobs:
       - uses: actions/checkout@v4
       - uses: ./.github/actions/setup-rust
         with:
-          targets: aarch64-unknown-linux-gnu armv7-unknown-linux-gnueabihf x86_64-unknown-linux-gnu
+          targets: aarch64-unknown-linux-musl armv7-unknown-linux-musleabihf x86_64-unknown-linux-musl
       - uses: taiki-e/install-action@v2
         with:
           tool: cross
       - name: Build release binaries
-        env:
-          # Enable statically-linked libc runtime
-          RUSTFLAGS: "-C target-feature=+crt-static"
         run: |
           set -xe