Currently,
cd test/xray/TestCases/Posix $build/bin/llvm-lit fdr-thread-order.cc
fails because rm fdr-thread-order.* deletes the .cc file.
This patch uses:
- %t as temporary directory name containing log files
- %t.exe as executable name
it does not delete %t after the test finishes for debugging convenience
if something goes wrong. This matches the behavior of many other LLVM
components.