Add OutOfMemory log helper

Add a special LOG_OOM() function to log all OutOfMemory errors (i.e.
allocations returning NULL).

app/src/sys/unix/file.c

@@ -7,6 +7,8 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+#include "util/log.h"
+
 bool
 sc_file_executable_exists(const char *file) {
     char *path = getenv("PATH");
@@ -24,7 +26,10 @@ sc_file_executable_exists(const char *file) {
         size_t dir_len = strlen(dir);
         char *fullpath = malloc(dir_len + file_len + 2);
         if (!fullpath)
+        {
+            LOG_OOM();
             continue;
+        }
         memcpy(fullpath, dir, dir_len);
         fullpath[dir_len] = '/';
         memcpy(fullpath + dir_len + 1, file, file_len + 1);