Fix android.security.cts.FileDescriptorTest#testCLOEXEC

When ART is mainline, it will create memFd boot-image-methods.art
without MFD_CLOEXEC.
Add MFD_CLOEXEC flag when create boot-image-methods.art memFd.

Bug: 197498527
Test: run cts CtsSecurityTestCases pass

Merged-In: If941c036f7adb598d67ec2b2c5bc4cb24994e3a1
(cherry picked from commit 3326fcea1ead5d5d360a053704faad27b6dd8c40)
Change-Id: Icfc2420e8e9d3f61f5e3f2eb5bfc53108c2c251b
(cherry picked from commit 0857789b5b09bccc977f712a071c7b68bfccae05)
2 files changed