RISC-V: unit test failures on GCC

[namhyung]

Like in this comment, currently uftrace gets SIG failure (meaning it's terminated by a signal) for every unit test function on RISC-V when it's built by gcc. Clang built versions are fine, so it should be a compiler issue.

The assembly output shows that the uftrace.unit_test section didn't have any data and filled with 0s. This info is needed for the unittest binary to find the test name and function address to run. We can skip the test with 0 value to prevent the segfault, but it'd be meaningless when it cannot run any tests. So I'd like to keep this issue open and to track any progress on it.

$ nm tests/unittest | grep framework
000000000000eef4 T func_unittest_framework
00000000000940c8 D test_unittest_framework

$ hexdump -C -s 0x940c8 -n 16 tests/unittest
000940c8  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000940d8

[namhyung]

I've updated it to run unit tests on RISC-V. Please check check/riscv-test branch.