Hi,
No, it doesn't solve the build error.
The build error is related to the mellanox driver sources that you got from git.
What i explained compiles the native driver provided with FreeBSD 11.1
For now, there's no GA release for FreeBSD 11.1 it is certainly the reason the build failed.
I 've tried to workaround this problem by adding in the CFLAGS the path to the linx/errno.h CFLAGs = -I<path>, but the compilation failed at a later stage.
Conclusion:
For now, there's only this FReeBSD 11 build that is supported : FreeBSD 11 Current (v289420)
Marc