ThinLTO for libstd breaks the leak sanitizer

[alexcrichton]

Discovered in #46008 apparently building libstd with ThinLTO causes the proof-of-concept test of the leak sanitizer to test. The test exits successfully and doesn't print out anything about leaks. I'm going to turn the test off for now as the sanitizers are all unstable.

[hanna-kruppe]

cc #45220, could be the same issue. (since #45810 was merged, the assertion failure reported in #45220 has been replaced with silent out-of-bounds indexing, which could have arbitraily weird consequences)