CI: fix qt5 path for linux builds

Author: lateleite

appveyor.yml

@@ -7,9 +7,9 @@ image:
 environment:
   matrix:
     - BUILD_COMBO: linux-gcc
-      Qt5_DIR: "$HOME/Qt/5.14"
+      Qt5_DIR: "$HOME/Qt/5.14/gcc_64"
     - BUILD_COMBO: linux-clang
-      Qt5_DIR: "$HOME/Qt/5.14"
+      Qt5_DIR: "$HOME/Qt/5.14/clang_64"
     - BUILD_COMBO: windows-mingw
       Qt5_DIR: "C:\\Qt\\5.14\\mingw73_64"
     - BUILD_COMBO: windows-msvc