Fix memory leak on AST

    AST was leaking the singleton pointer.

Signed-off-by: Rafael Campos Nunes <rafaelnunes@engineer.com>

Author: rafaelcn

src/ast/general/ASTInfo.cpp

@@ -22,6 +22,10 @@ ASTInfo* ASTInfo::instance()
     return ASTInfo::_instance;
 }
 
+ASTInfo::~ASTInfo() {
+  delete _instance;
+}
+
 llvm::GlobalVariable* ASTInfo::get_index_ptr()
 {
     return __brain_index_ptr;

src/ast/general/ASTInfo.h

@@ -35,6 +35,7 @@ class ASTInfo
 public:
     ASTInfo(ASTInfo const&) = delete;
     ASTInfo& operator=(ASTInfo const&) = delete;
+    ~ASTInfo();
     /**
      * @brief Returns the instance of ASTInfo class if the member _instance is
      * nullptr, otherwise it creates a new ASTInfo object and returns it.