The removed get_machine function is no longer used since #21255.
Now that we are using Focal for Gitian building (glibc 2.31), we can user a newer introduced symbol, and include RISCV in this test.
Check both failure cases: - Use a glibc symbol from a version that is too new - Use a symbol from a library that is not in the allowlist And also check a conforming binary. Adding a similar check for Windows PE can be done in a separate PR.
Hennadii Stepanov