haproxy: Fix build for Linux
haproxy: Fix build for Linux

- When trying to build the bottle, it errored with the very helpful
  error message:
  ```
  Target 'linux2628' was removed from HAProxy 2.0 due to being irrelevant and
  often wrong. Please use 'linux-glibc' instead or define your custom target
  by checking available options using 'make help TARGET=<your-target>'.
```

Closes #14487.

Signed-off-by: Issy Long <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@issyl0.co.uk>

rwhogg/homebrew-core,Linuxbrew/homebrew-core,maxim-belkin/homebrew-core,Linuxbrew/homebrew-core,LinuxbrewTestBot/homebrew-core,LinuxbrewTestBot/homebrew-core,rwhogg/homebrew-core,maxim-belkin/homebrew-core