VirtualMemory: add missing header after 5d15d64ec8 (#4532)

Utilities/VirtualMemory.cpp:123:8: error: use of undeclared identifier 'errno'
                        if (errno != EEXIST)
                            ^
Utilities/VirtualMemory.cpp:123:17: error: use of undeclared identifier 'EEXIST'
                        if (errno != EEXIST)
                                     ^

Utilities/VirtualMemory.cpp

@@ -7,6 +7,7 @@
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/types.h>
 #endif