The change d80f856adf59 introduced a bug which allows using non Linux GCC compilers for Linux builds. This results in compilation errors like:
In file included from /home/vagrant/src/trusted-services/components/rpc/ffarpc/caller/linux/ffarpc_caller.c:8: /home/vagrant/src/trusted-services/deployments/ts-service-test/arm-linux/build/_deps/libts-build/_deps/linux_ffa_user_shim/arm_ffa_user.h:10: fatal error: linux/ioctl.h: No such file or directory