Merge branch 'cmake_glu' of https://github.com/swt2c/wxWidgets

Link with GLU when using EGL too in CMake build.

Also build all samples in the CMake CI builds.

See https://github.com/wxWidgets/wxWidgets/pull/2543

.github/workflows/ci_cmake.yml

@@ -52,6 +52,7 @@ jobs:
           - name: Ubuntu 18.04 wxGTK 3
             runner: ubuntu-18.04
             cmake_generator: Unix Makefiles
+            cmake_samples: ALL
           - name: macOS 10.15 wxOSX
             runner: macos-10.15
             cmake_generator: Xcode

build/cmake/init.cmake

@@ -411,7 +411,7 @@ if(wxUSE_GUI)
         else()
             find_package(OpenGL)
             if(WXGTK3 AND OpenGL_EGL_FOUND AND wxUSE_GLCANVAS_EGL)
-                set(OPENGL_LIBRARIES OpenGL::OpenGL OpenGL::EGL)
+                set(OPENGL_LIBRARIES OpenGL::OpenGL OpenGL::GLU OpenGL::EGL)
                 find_package(WAYLANDEGL)
                 if(WAYLANDEGL_FOUND AND wxHAVE_GDK_WAYLAND)
                     list(APPEND OPENGL_LIBRARIES ${WAYLANDEGL_LIBRARIES})