Demonstrate use of a hermetic bazel riscv-64 toolchain on a Fedora 40 host

[thixotropist]

The existing riscv-64 toolchains were built on a Fedora 39 host and include Fedora 39 system libraries. Show that the toolchain and system libraries can be used on a Fedora 40 host.

Specifically:

• show that ./generateInternalExemplars.py completes a riscv64 build with no test errors on a Fedora 40 host
• add integration/regression tests to help identify the root cause of any future hermeticity failures

At present ./generateInternalExemplars.py fails 5 tests out of 8, throwing segmentation faults during cross-compilation with little clarity on the root cause. Similar errors in the past have been due to a lack of hermeticity, where child processes started by gcc (as or ld) have failed to find the system sharable library versions they were built against.

[thixotropist]

Resolved with commit 1daa3634cf21. This commit relies on the host computer for libc.so and dynamic loader libraries, while continuing to import other libraries needed for the gcc C and C++ compilers.