CursorWindow.cpp: replace dup() with fcntl(F_DUPFD_CLOEXEC)

Replace calls to dup() with fcntl(F_DUPFD_CLOEXEC). The only difference
between the two is that O_CLOEXEC is set on the newly duped file
descriptor. This helps address file descriptor leaks crossing an exec()
boundary.

Test: compiles and boots
Bug: 120983106
Change-Id: Icc2ff2f7f398905aa8283c8797898114d34a9829

libs/androidfw/CursorWindow.cpp

@@ -94,7 +94,7 @@ status_t CursorWindow::createFromParcel(Parcel* parcel, CursorWindow** outCursor
         if (size < 0) {
             result = UNKNOWN_ERROR;
         } else {
-            int dupAshmemFd = ::dup(ashmemFd);
+            int dupAshmemFd = ::fcntl(ashmemFd, F_DUPFD_CLOEXEC, 0);
             if (dupAshmemFd < 0) {
                 result = -errno;
             } else {