Adding object elevation param.

Quick attempt to build with MinGW 7.3. Successful compile, failed linking

src/avrdude/CMakeLists.txt

@@ -66,7 +66,7 @@ set(AVRDUDE_SOURCES
     avrdude-slic3r.hpp
     avrdude-slic3r.cpp
 )
-if (WIN32)
+if (MSVC)
     set(AVRDUDE_SOURCES ${AVRDUDE_SOURCES}
         windows/unistd.cpp
         windows/getopt.c

src/avrdude/main.c

@@ -43,7 +43,7 @@
 #include <ctype.h>
 #include <sys/types.h>
 
-#if !defined(WIN32NATIVE)
+#if !defined(WIN32NATIVE) || defined(__GNUC__)
 #  include <sys/time.h>
 #  include <sys/types.h>
 #  include <sys/stat.h>