Revert commit f4988f5b

This seems to have caused some regressions by causing a flaky failure in some
cases.  Revert the change to enable investigation.

PiperOrigin-RevId: 459331687
Change-Id: Iaa4e4bfcb3013a75a2cd72768d980ac5e450f70c

absl/debugging/internal/stacktrace_riscv-inl.inc

@@ -159,21 +159,6 @@ static void ** NextStackFrame(void **old_frame_pointer, const void *uc) {
     const uintptr_t max_size = STRICT_UNWINDING ? 100000 : 1000000;
     const uintptr_t frame_size =
         ComputeStackFrameSize(old_frame_pointer, new_frame_pointer);
-
-    // If we have a alternate signal stack, the stack pointer may not be
-    // contiguous. In such a case, we can simply skip the check and assume that
-    // the non-contiguity is permissible.
-    if (frame_size == kUnknownFrameSize) {
-      assert(old_frame_pointer >= new_frame_pointer);
-
-      stack_t ss{};
-      if (sigaltstack(nullptr, &ss) == 0) {
-        if (ss.ss_flags & SS_DISABLE)
-          return nullptr;
-        return new_frame_pointer;
-      }
-    }
-
     if (frame_size == kUnknownFrameSize || frame_size > max_size)
       return nullptr;
   }