Fix modules build, guard on _WIN32 instead of _MSC_VER

Author: jeremy-rifkin

include/cpptrace/utils.hpp

@@ -65,7 +65,7 @@ CPPTRACE_BEGIN_NAMESPACE
     }
 
     // dbghelp
-    #ifdef _MSC_VER
+    #ifdef _WIN32
      CPPTRACE_EXPORT void load_symbols_for_file(const std::string& filename);
     #endif
 CPPTRACE_END_NAMESPACE

src/cpptrace.cppm

@@ -103,5 +103,7 @@ CPPTRACE_BEGIN_NAMESPACE
         export using cpptrace::experimental::set_dwarf_resolver_disable_aranges;
     }
 
-    export using cpptrace::load_symbols_for_file;
+    #ifdef _WIN32
+     export using cpptrace::load_symbols_for_file;
+    #endif
 CPPTRACE_END_NAMESPACE

src/utils.cpp

@@ -90,7 +90,7 @@ CPPTRACE_BEGIN_NAMESPACE
         std::set_terminate(terminate_handler);
     }
 
-    #if defined(_MSC_VER) && !defined(CPPTRACE_GET_SYMBOLS_WITH_DBGHELP)
+    #if defined(_WIN32) && !defined(CPPTRACE_GET_SYMBOLS_WITH_DBGHELP)
      void load_symbols_for_file(const std::string&) {
          // nop
      }