fix(ci): zgf — purge committed cpp/build artifacts; ignore build/

Unblocks PR #30 cpp/go/python/rust binding tests which were failing
on stale CMakeCache.txt with absolute path /Users/playra/trinity-w1/...
vs Linux runner /home/runner/work/... The zig binding already passes
(mlugg/setup-zig fix verified), this removes the dirty-tree blocker
for the remaining 4 language jobs.

Also adds **/build/, *.o/.a/.so/.dylib, CMakeCache.txt, CMakeFiles/
to .gitignore to prevent recurrence.

Author: gHashTag

.gitignore

@@ -4,3 +4,14 @@ zig/
 rust/target/
 rust/*.rs
 rust/test_nan
+
+# Build artifacts
+cpp/build/
+**/build/
+*.o
+*.a
+*.so
+*.dylib
+CMakeCache.txt
+CMakeFiles/
+