Fix: compilation failed on gcc 10.2 due to missing include. (#11300)

'_exit' is defined in 'unistd.h'.

src/os/unix/crashlog_unix.cpp

@@ -23,10 +23,6 @@
 #	include <execinfo.h>
 #endif
 
-#if defined(__NetBSD__)
-#include <unistd.h>
-#endif
-
 #ifdef WITH_UNOFFICIAL_BREAKPAD
 #	include <client/linux/handler/exception_handler.h>
 #endif
@@ -35,6 +31,8 @@
 #	include <emscripten.h>
 /* We avoid abort(), as it is a SIGBART, and use _exit() instead. But emscripten doesn't know _exit(). */
 #	define _exit emscripten_force_exit
+#else
+#include <unistd.h>
 #endif
 
 #include "../../safeguards.h"