fix(desktop): restore explicit target to Linux builds (#18169)

Commit a3e654d (https://github.com/bitwarden/clients/pull/16053) removed explicit --target flags from the Linux desktop build workflow when removing musl support. This change inadvertently broke the build.js binary distribution logic, which only copies the desktop_proxy binary to the dist directory when an explicit target is specified. Without this binary in the expected location (/opt/Bitwarden/desktop_proxy), browser integration fails on Linux.

This fix restores explicit --target flags using gnu triplets instead of the previously removed musl triplets. The x64 build now uses --target=x86_64-unknown-linux-gnu and the arm64 build uses --target=aarch64-unknown-linux-gnu, ensuring build.js properly distributes the desktop_proxy binary and restoring browser integration functionality on Linux desktop.

.github/workflows/build-desktop.yml

@@ -265,7 +265,7 @@ jobs:
         # Note: It is important that we use the release build because some compute heavy
         # operations such as key derivation for oo7 on linux are too slow in debug mode
         run: |
-          node build.js --release
+          node build.js --target=x86_64-unknown-linux-gnu --release
 
       - name: Build application
         run: npm run dist:lin
@@ -428,7 +428,7 @@ jobs:
         # Note: It is important that we use the release build because some compute heavy
         # operations such as key derivation for oo7 on linux are too slow in debug mode
         run: |
-          node build.js --release
+          node build.js --target=aarch64-unknown-linux-gnu --release
 
       - name: Check index.d.ts generated
         if: github.event_name == 'pull_request' && steps.cache.outputs.cache-hit != 'true'