libogc's EXI functions return '1 on success, <=0 on error', but every call
site tested '== 0'. A -1 error return therefore read as success, so a failed
EXI_Lock or EXI_Select would fall through and the subsequent transfer would
produce garbage reported as a misleading test failure rather than an EXI
error. All six call sites now test <= 0.
Also retries EXI_Lock for ~100 ms: it fails outright rather than blocking when
another subsystem holds the channel, and Swiss or a libogc driver may hold it
briefly -- without the retry a transient collision surfaces as a test failure.
Builds clean with devkitPPC 16.1.0 / GCC 16, no warnings: 172 KB .dol.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Roflin
d8725392a5