Issue electron-userland#7500: Use update-alternatives instead of syml…

…inks to executable if available.

Where possible, use `update-alternatives` instead to avoid hardcoding links in Linux.
This will allow for downstream users to specify paths to their own executables
with higher priority if they wish.

Backwards compatibility is preserved by still using the symlinking route if
the command `update-alternatives` is not available.

packages/app-builder-lib/templates/linux/after-install.tpl

@@ -1,7 +1,11 @@
 #!/bin/bash
 
 # Link to the binary
-ln -sf '/opt/${sanitizedProductName}/${executable}' '/usr/bin/${executable}'
+if type update-alternatives 2>/dev/null >&1; then
+   update-alternatives --install '/usr/bin/${executable}' '${executable}' '/opt/${sanitizedProductName}/${executable}' 100
+else
+    ln -sf '/opt/${sanitizedProductName}/${executable}' '/usr/bin/${executable}'
+fi
 
 # SUID chrome-sandbox for Electron 5+
 chmod 4755 '/opt/${sanitizedProductName}/chrome-sandbox' || true

packages/app-builder-lib/templates/linux/after-remove.tpl

@@ -1,4 +1,8 @@
 #!/bin/bash
 
 # Delete the link to the binary
-rm -f '/usr/bin/${executable}'
+if type update-alternatives >/dev/null 2>&1; then
+    update-alternatives --remove '${executable}' '/usr/bin/${executable}'
+else
+    rm -f '/usr/bin/${executable}'
+fi