[XRay][test] Mark fdr-mode.cpp test as unsupported for RISC-V

Commit c6f501d479e8 fixed an issue where some tests were incorrectly
marked as unsupported for a bootstrapping build. This exposed in our
'slow' full-bootstrap qemu-system CI that the fdr-mode.cpp fails on
RISC-V. We mark it as unsupported. I believe _xray_ArgLoggerEntry needs
to be implemented in xray_trampoline_risc*.S for this to work.

NOKEYCHECK=True
GitOrigin-RevId: 8a53c01b67969de63be8082e08eb91e294de20ac
1 file changed