More fixes for compile-time warnings in equix and hashx

This addresses issue #40800 and a couple other problems I noticed while
trying to reproduce that one.

The original issue is just a missing cast to void* on the args of
__builtin___clear_cache(), and clang is picky about the implicit cast
between what it considers to be char of different signedness. Original
report is from MacOS but it's also reproducible on other clang targets.

The cmake-based original build system for equix and hashx was a handy
way to run tests, but it suffered from some warnings due to incorrect
application of include_directories().

And lastly, there were some return codes from hashx_exec() that get
ignored on equix when asserts are disabled. It bugged me too much to
just silence this with a (void) cast, since even though this is in the
realm of low-likelyhood programming errors and not true runtime errors, I
don't want to make it easy for the hashx_exec() wrappers to return
values that are dangerously wrong if an error is ignored. I made sure
that even if asserts are disabled, we return values that will cause the
solver and verifier to both fail to validate a potential solution.

Signed-off-by: Micah Elizabeth Scott <beth@torproject.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/changes/ticket40800 b/changes/ticket40800
new file mode 100644
index 0000000000..e2ebc80ee8
--- /dev/null
+++ b/changes/ticket40800
@@ -0,0 +1,3 @@
+  o Minor feature (hs):
+    - Fix compiler warnings in equix and hashx when building with clang.
+      Closes ticket 40800.