After the update to kernel 4.14.27, out of tree module builds started failing.
I'm using poky's meta-skeleton hello-mod recipe as an example.

Steps to re-create
------------------
These steps use meta-intel rt kernel 4.14.40 
$ git clone -b rocko git://git.yoctoproject.org/poky
$ git clone -b rocko git://git.yoctoproject.org/metal-intel
$ source poky/oe-init-build-env
$ bitbake-layers add-layer ../poky/meta-skeleton/
$ bitbake-layers add-layer ../meta-intel/
$ cat <<EOF >> conf/local.conf
MACHINE = "intel-corei7-64"
PREFERRED_PROVIDER_virtual/kernel = "linux-intel-rt"
PREFERRED_VERSION_linux-intel-rt = "4.14%"
EOF
$ bitbake hello-mod
...
| make -C /path/to/build/tmp/work-shared/intel-corei7-64/kernel-source M=/media/md126p1/yocto/hbruce/rocko/kmod-bug/build/tmp/work/intel_corei7_64-poky-linux/hello-mod/0.1-r0
| make[1]: Entering directory '/path/to/build/tmp/work-shared/intel-corei7-64/kernel-source'
| make[2]: Entering directory '/path/to/build/tmp/work-shared/intel-corei7-64/kernel-build-artifacts'
| make[3]: *** No rule to make target 'tools/objtool/objtool', needed by '/path/to/build/tmp/work/intel_corei7_64-poky-linux/hello-mod/0.1-r0/hello.o'.  Stop.
...
Summary: 1 task failed:
  /path/to/poky/meta-skeleton/recipes-kernel/hello-mod/hello-mod_0.1.bb:do_compile
Summary: There were 2 ERROR messages shown, returning a non-zero exit code.

Workaround
----------
Follow above steps but revert to kernel 4.14.24
$ cd ../meta-intel
$ git checkout 91ad013e655d56889efe9b65c1c7691dea5034c4
HEAD is now at 91ad013... linux-intel-rt_4.14: update to v4.14.24
$ cd ../build
$ bitbake hello-mod
NOTE: Tasks Summary: Attempted 527 tasks of which 493 didn't need to be rerun and all succeeded.