build failure on musl due to use of glibc internal __bswap_16

[rofl0r]

Godot version: 3.0.6 stable
OS/device including version: sabotage linux x86_64 using musl libc
Issue description:

platform/x11/joypad_linux.cpp: In member function 'void JoypadLinux::open_joypad(const char*)':
platform/x11/joypad_linux.cpp:370:52: error: '__bswap_16' was not declared in this scope
   sprintf(uid, "%04x%04x", __bswap_16(inpid.bustype), 0);

maybe this should be added to #20037

[rofl0r]

any libc function names starting with __ are not for external use.