Minor optimisations and bug fixes

Fix bug in mt_mpmc.c, in Linux mutexes are not recursive.
Add arena_trim_string() to the arena API
Removing arena->path, now paths are pushed to arena->metadata
Replacing fe->owner[128] with char *owner; the owner is not pushed as a
string to arena->metadata and trimed with arena_trim_string()
Improving cache locality in arena->metadata, the memory layout is not
fe; fe->path; fe->owner.
Cache aligning all arenas except HasherContext->arena to sizeof(void *).
Pushing elements one by one instead of snprintf() in finalize_file() and
hash_worker().
Getting the full path of current directory instead of "."
Fixing bug in path formating, this allow us to remove normalize_path()
from the hot loop.

mt_mpmc.h

@@ -1,4 +1,4 @@
-#pragma once 
+#pragma once
 
 #include "base.h"
 
@@ -214,19 +214,27 @@ static void mpmc_producers_finished(MPMCQueue *q, u8 consumer_count) {
 /* Done */
 /* ----------------------------------------------------------- */
 static void mpmc_task_done(MPMCQueue *q, u8 consumer_count) {
+
+  bool finished = false;
+
   mtx_lock(&q->lock);
 
   if (--q->work_count == 0) {
-     mpmc_producers_finished(q, consumer_count);
+    finished = true;
   }
 
   mtx_unlock(&q->lock);
+
+  if (finished) {
+    mpmc_producers_finished(q, consumer_count);
+  }
 }
 
 /* ----------------------------------------------------------- */
 /* MPMC Cleanup */
 /* ----------------------------------------------------------- */
-// static void mpmc_finish(MPMCQueue *q) { // Comment to prevent warning: unused function
+// static void mpmc_finish(MPMCQueue *q) { // Comment to prevent warning: unused
+// function
 //   if (!q) return;
 //
 //   if (q->slots) {