CI: disable (riscv64, debug)

There are several issues with riscv64 debug:

  - The QEMU hang can be solved disabling `DEBUG_WW_MUTEX_SLOWPATH` /
    `DEBUG_LOCK_ALLOC` / `LOCKDEP`.

  - kallsyms needing 5 passes or oscillating between 2 sizes (#502).
    Needs a deeper look.

For the moment, let's exclude (riscv64, debug) from the matrix to avoid
holding the sync since others are waiting.

Signed-off-by: Miguel Ojeda <[email protected]>

Author: ojeda

.github/workflows/ci.yaml

@@ -22,6 +22,9 @@ jobs:
           # arm 32-bit gcc not yet supported
           - arch: arm
             toolchain: gcc
+          # riscv64 debug (see #500 and #502).
+          - arch: riscv64
+            config: debug
           # Exclude `LLVM=1` where not supported.
           - arch: ppc64le
             toolchain: llvm