clang-tidy: enable bugprone-multi-level-implicit-pointer-conversion

The default clang version in nixos 25.05 was llvm 19, we are now even
past that

Change-Id: Ieb62616fb87c4d2a8d892136a7164822aa1eceb6

.clang-tidy

@@ -14,8 +14,6 @@ Checks:
   - -bugprone-unchecked-optional-access
     # many warnings, seems like a questionable lint
   - -bugprone-branch-clone
-    # extremely noisy before clang 19: https://github.com/llvm/llvm-project/issues/93959
-  - -bugprone-multi-level-implicit-pointer-conversion
     # we don't compile out our asserts
   - -bugprone-assert-side-effect
     # FIXME(jade): figure out if this warning is any good

lix/libcmd/repl-interacter.cc

@@ -48,7 +48,7 @@ char ** copyCompletions(const StringSet& possible)
             if (vp) {
                 while (--ac >= 0)
                     free(vp[ac]);
-                free(vp);
+                free(static_cast<void *>(vp));
             }
             throw Error("allocation failure");
         }

lix/libexpr/eval.cc

@@ -291,14 +291,14 @@ EvalMemory::EvalMemory()
 {
     assert(libexprInitialised);
 #if HAVE_BOEHMGC
-    GC_add_roots(gcCache, gcCache + CACHES);
+    GC_add_roots(static_cast<void *>(gcCache), static_cast<void *>(gcCache + CACHES));
 #endif
 }
 
 EvalMemory::~EvalMemory()
 {
 #if HAVE_BOEHMGC
-    GC_remove_roots(gcCache, gcCache + CACHES);
+    GC_remove_roots(static_cast<void *>(gcCache), static_cast<void *>(gcCache + CACHES));
 #endif
 }