"/sys/conf/kmod.mk", line 111: Malformed conditional (${MK_CLANG_IS_CC}

On one of my FreeBSD 10.0-CURRENT boxes I receive this morning this
error message as shown below.

I need to add, that I compiled the shown nvidia-driver hours ago on all
FreeBSD 9.0-STABLE boxes with the same settings and I compiled the
driver just two days before the same way I tried it this morning. What's
wrong?

Some unexpected breakage? Then this is my shout to the community.

Message below.

Regards and thanks in advance,
Oliver

===>  Vulnerability check disabled, database not found
===>  License NVIDIA accepted by the user
===>  Found saved configuration for nvidia-driver-295.20
===>  Extracting for nvidia-driver-295.20
=> SHA256 Checksum OK for NVIDIA-FreeBSD-x86_64-295.20.tar.gz.
===>  Patching for nvidia-driver-295.20
===>   nvidia-driver-295.20 depends on file:
/usr/local/libdata/pkgconfig/xorg-server.pc - found
===>   nvidia-driver-295.20 depends on shared library: GL.1 - found
===>  Configuring for nvidia-driver-295.20
===>  Building for nvidia-driver-295.20
===> src (all)
"/sys/conf/kmod.mk", line 111: Malformed conditional (${MK_CLANG_IS_CC}
== "no" && ${CC:T:Mclang} != "clang")
"/sys/conf/kmod.mk", line 115: if-less endif
"/sys/conf/kern.mk", line 18: Malformed conditional (${MK_CLANG_IS_CC}
!= "no" || ${CC:T:Mclang} == "clang")
"/sys/conf/kern.mk", line 31: if-less endif
"/sys/conf/kern.mk", line 101: Malformed conditional (${MK_CLANG_IS_CC}
== "no" && ${CC:T:Mclang} != "clang")
"/sys/conf/kern.mk", line 109: if-less endif
make: fatal errors encountered -- cannot continue
*** [all] Error code 1

Stop in /usr/ports/x11/nvidia-driver/work/NVIDIA-FreeBSD-x86_64-295.20.