Fix MSVC compiler errors (#3742) (#3746)

docs/CONTRIBUTORS

@@ -65,6 +65,7 @@ Kamil Rakoczy
 Kanad Kanhere
 Keith Colbert
 Kevin Kiningham
+Kritik Bhimani
 Krzysztof Bieganski
 Kuba Ober
 Larry Doolittle

src/V3Os.cpp

@@ -78,7 +78,7 @@ VL_DEFINE_DEBUG_FUNCTIONS;
 string V3Os::getenvStr(const string& envvar, const string& defaultValue) {
 #if defined(_MSC_VER)
     // Note: MinGW does not offer _dupenv_s
-    const char* const envvalue = nullptr;
+    const char* envvalue = nullptr;
     _dupenv_s(&envvalue, nullptr, envvar.c_str());
     if (envvalue != nullptr) {
         const std::string result{envvalue};

src/V3TraceDecl.cpp

@@ -285,7 +285,7 @@ private:
                 // Recurse into data type of the signal. The visit methods will add AstTraceDecls.
                 iterate(m_traVscp->varp()->dtypep()->skipRefToEnump());
                 // Cleanup
-                if (m_traValuep) VL_DO_DANGLING(m_traValuep->deleteTree(), m_traValuep);
+                if (m_traValuep) VL_DO_CLEAR(m_traValuep->deleteTree(), m_traValuep = nullptr);
             }
         }
         pathAdjustor.unwind();