libutil/windows: only define headers/code if we are actually on windows

all those includes otherwise break linters.

src/libutil/windows/processes.cc

@@ -23,6 +23,8 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#ifdef WIN32
+
 #define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 
@@ -386,3 +388,5 @@ int execvpe(const wchar_t * file0, const wchar_t * const argv[], const wchar_t *
 }
 
 }
+
+#endif