[cef] Fix cef build for renesas

[cef] Fix cef build for renesas

The logic to check if the current toolchain was target or host was wrong and a
linker error(for libvk_swiftshader.so) started to happen after 29449 and 29419:

aarch64-agl-linux-ld.lld: error:
  .../clang/14.0.6/lib/linux/libclang_rt.builtins-x86_64.a(clear_cache.c.o)
  is incompatible with elf64-littleaarch64

The fix makes use of the chromium gn variable created for checking if the
current toolchain is a target build.

Bug-AGL: SPEC-4976

Signed-off-by: Roger Zanoni <rzanoni@igalia.com>
Change-Id: Ibd6c6ab9c85951a2b8933c7c1c7107c3f94b59ec
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl-demo/+/29420
ci-image-build: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Tested-by: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>