[lldb][CMake] Fix linking of gdb-remote when LLVM_ENABLE_ZLIB is ON

When LLVM_ENABLE_ZLIB is ON gdb-remote should link against ZLIB::ZLIB.

This fixes
```
/mnt/b/yoe/master/build/tmp/hosttools/ld: lib/liblldbPluginProcessGDBRemote.a(GDBRemoteCommunication.cpp.o): in function `lldb_private::process_gdb_remote::GDBRemoteCommunication::DecompressPacket() [clone .localalias]':
GDBRemoteCommunication.cpp:(.text._ZN12lldb_private18process_gdb_remote22GDBRemoteCommunication16DecompressPacketEv+0x59a): undefined reference to `inflateInit2_'
/mnt/b/yoe/master/build/tmp/hosttools/ld: GDBRemoteCommunication.cpp:(.text._ZN12lldb_private18process_gdb_remote22GDBRemoteCommunication16DecompressPacketEv+0x5af): undefined reference to `inflate'
```

Reviewed By: JDevlieghere, MaskRay

Differential Revision: https://reviews.llvm.org/D119186