The configure script shipped by screen uses the presence of `elf.h` and `-lelf`
as indicator for an SVR4 system which implies a `#define BUGGYGETLOGIN`.

The SVR4 `getlogin()` replacement function does not compile with a musl
toolchain and we do not want it anyway, so patch configure to remove the broken
SVR4 detection logic.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>