[Bug]: absl_hashtablez_sampler_test and absl_cordz_sample_token_test fail on riscv64-linux-gnu

### Describe the issue

seen with the Debian build of 20260107.0, but not with the Ubuntu build, where these tests succeed:

99% tests passed, 2 tests failed out of 232

Total Test time (real) = 306.65 sec

The following tests FAILED:
50 - absl_hashtablez_sampler_test (SEGFAULT)
207 - absl_cordz_sample_token_test (SEGFAULT)
Errors while running CTest
make[2]: *** [Makefile:74: test] Error 8

### Steps to reproduce the problem

run the testsuite on Debian unstable

### What version of Abseil are you using?

20260107.0

### What operating system and version are you using?

Debian unstable

### What compiler and version are you using?

GCC 15.2, updated from the gcc-15 branch

### What build system are you using?

cmake 4.2.3

### Additional context

_No response_