EAGL: Define ANGLE_ENABLE_EAGL in build system ANGLE_ENABLE_EAGL is a "build system" decision. Set this and new variable ANGLE_ENABLE_CGL in BUILD.gn file. This is consistent with the other backends. Remove ANGLE_CPU_ARM64. This was used to do ANGLE_ENABLE_EAGL=TRUE when on Catalyst. Instead, let the build system set this. For ANGLE/Chrome buildsystem, this is not set, as Catalyst is not implemented. For WebKit, this should be set at WebKit build settings. Replace `defined(ANGLE_PLATFORM_MACCATALYST) && defined(ANGLE_CPU_ARM64)` with simpler expression: `defined(ANGLE_ENABLE_EAGL)`. Replace `defined(ANGLE_PLATFORM_MACOS) || defined(ANGLE_PLATFORM_IOS)` with simpler expression: `defined(ANGLE_PLATFORM_APPLE)`. Bug: angleproject:8121 Change-Id: I3a0bbabb4347ad11f693e3f7c336ff12f66203d7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4404160 Commit-Queue: Kimmo Kinnunen <kkinnunen@apple.com> Reviewed-by: Dan Glastonbury <djg@apple.com> Reviewed-by: Kenneth Russell <kbr@chromium.org>