[compiler-rt][lsan] Increase libdl_deadlock test timeout

We have been seeing this test fail intermittently on our
2 stage AArch64 bot.

As far back as https://lab.llvm.org/buildbot/#/builders/53/builds/2694

Likely due to a lack of resources at certain times on the
shared machine. Up the time limit to give us some more room.

(this limit only applies to the watchdog thread, so if the
test passes then it won't take 20s)