Vulkan: Fix build issue in vulkan display/headless backend. In Linux + Vulkan display/headless backend, angle tests such as angle_unittests/angle_perftests/angle_white_box_perf_tests could not be compiled successfully, fix build issues on vulkan display/headless backend in angle tests. 1. Add EGL_NO_X11 flag into vulkan display/headless backend. 2. Disable angle_white_box_perf_tests on vulkan display/headless backend. Bug: angleproject:5260 Change-Id: I579aee8b0bfaa4c0d7fdf9a6df91c1b78ec4373e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2585256 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>