Change stringify utility to avoid a compiler bug in GitLab/CI

This is strange, I cannot reproduce this compilation issue using
various installations of clang-10 ...

src/language/node_processor/AffectationProcessor.hpp

@@ -98,7 +98,11 @@ class AffectationExecutor final : public IAffectationExecutor
     if constexpr (m_is_defined) {
       auto stringify = [](auto&& value) {
         std::ostringstream os;
+        if constexpr (std::is_same_v<std::decay_t<decltype(value)>, bool>) {
           os << std::boolalpha << value;
+        } else {
+          os << value;
+        }
         return os.str();
       };
 
@@ -445,7 +449,11 @@ class AffectationToTupleProcessor final : public AffectationToDataVariantProcess
   {
     auto stringify = [](auto&& value) {
       std::ostringstream os;
+      if constexpr (std::is_same_v<std::decay_t<decltype(value)>, bool>) {
         os << std::boolalpha << value;
+      } else {
+        os << value;
+      }
       return os.str();
     };
 
@@ -500,7 +508,11 @@ class AffectationToTupleFromListProcessor final : public AffectationToDataVarian
   {
     auto stringify = [](auto&& value) {
       std::ostringstream os;
+      if constexpr (std::is_same_v<std::decay_t<decltype(value)>, bool>) {
         os << std::boolalpha << value;
+      } else {
+        os << value;
+      }
       return os.str();
     };
 
@@ -563,7 +575,11 @@ class AffectationToTupleFromListProcessor final : public AffectationToDataVarian
   {
     auto stringify = [](auto&& value) {
       std::ostringstream os;
+      if constexpr (std::is_same_v<std::decay_t<decltype(value)>, bool>) {
         os << std::boolalpha << value;
+      } else {
+        os << value;
+      }
       return os.str();
     };