[angle] Fix regressions introduced in #4862:

[ras0219-msft]

Reintroduces the unofficial:: targets.

Use PREFER_NINJA.

Small simplifications/modernizations.

[qis]

Awesome! The unofficial::angle part works well, but I still have to link against X11::X11 and dl manually:

if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
  find_package(X11 REQUIRED)
  if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.14.0")
    target_link_libraries(${PROJECT_NAME} PUBLIC X11::X11 dl)
  else()
    target_include_directories(${PROJECT_NAME} PUBLIC ${X11_INCLUDE_DIR})
    target_link_libraries(${PROJECT_NAME} PUBLIC ${X11_LIBRARIES} dl)
  endif()
endif()

find_package(unofficial-angle CONFIG REQUIRED)
target_link_libraries(${PROJECT_NAME} PUBLIC unofficial::angle::libEGL unofficial::angle::libGLESv2)

Since it's an unofficial config, shouldn't we add it to the dependencies? I can send you a patch, but it won't have OSX support in it.

[ras0219-msft]

@qis That'd be great! Incremental progress is still progress :)