Fix build using mingw

Credit to t-hey

Author: nyalldawson

src/app/main.cpp

@@ -477,7 +477,7 @@ int main( int argc, char *argv[] )
   signal( SIGXFSZ, qgisCrash );
 #endif
 
-#ifdef Q_OS_WIN
+#ifdef _MSC_VER
   SetUnhandledExceptionFilter( QgsCrashHandler::handle );
 #endif
 

src/core/qgsapplication.cpp

@@ -847,7 +847,7 @@ QString QgsApplication::userFullName()
   //fall back to login name
   if ( sUserFullName.isEmpty() )
     sUserFullName = userLoginName();
-#elif defined(Q_OS_ANDROID)
+#elif defined(Q_OS_ANDROID) || defined(__MINGW32__)
   sUserFullName = "Not available";
 #else
   struct passwd *p = getpwuid( getuid() );

src/core/qgsfeaturerequest.cpp

@@ -387,6 +387,8 @@ bool QgsFeatureRequest::OrderByClause::prepare( QgsExpressionContext *context )
   return mExpression.prepare( context );
 }
 
+QgsFeatureRequest::OrderBy::OrderBy() = default;
+
 QgsFeatureRequest::OrderBy::OrderBy( const QList<QgsFeatureRequest::OrderByClause> &other )
 {
   Q_FOREACH ( const QgsFeatureRequest::OrderByClause &clause, other )

src/core/qgsfeaturerequest.h

@@ -225,7 +225,7 @@ class CORE_EXPORT QgsFeatureRequest
         /**
          * Create a new empty order by
          */
-        CORE_EXPORT OrderBy() = default;
+        CORE_EXPORT OrderBy();
 
         /**
          * Create a new order by from a list of clauses