After starting ec-utils in factory-eve branch [+minilayout],
make buildall fails with:

======= building cr50
make --no-print-directory BOARD=cr50 V=
./util/getversion.sh: line 86: pushd: ../../third_party/tpm2: No such file or directory
./util/getversion.sh: line 95: popd: directory stack empty
./util/getversion.sh: line 86: pushd: ../../third_party/cryptoc: No such file or directory
./util/getversion.sh: line 95: popd: directory stack empty
make obj=/mnt/host/source/src/platform/ec/build/cr50/tpm2 EMBEDDED_MODE=1 OBJ_PREFIX=Tpm2_ -C
make: option requires an argument -- 'C'
Usage: make [options] [target] ...

Going further after manually doing 
cros_workon --board=eve start tpm2

But fails with:
======= building cr50
make --no-print-directory BOARD=cr50 V=
./util/getversion.sh: line 86: pushd: ../../third_party/cryptoc: No such file or directory
./util/getversion.sh: line 95: popd: directory stack empty
make obj=/mnt/host/source/src/platform/ec/build/cr50/tpm2 EMBEDDED_MODE=1 OBJ_PREFIX=Tpm2_ -C /mnt/host/source/src/third_party/tpm2
make[3]: '/mnt/host/source/src/platform/ec/build/cr50/tpm2/libtpm2.a' is up to date.
make obj=/mnt/host/source/src/platform/ec/build/cr50/cryptoc SUPPORT_UNALIGNED=1 \
        CONFIG_UPTO_SHA512=y -C
make: option requires an argument -- 'C'

Adding cryptoc is more difficult as there are no cryptoc ebuild.
I manually added src/third_party/cryptoc to /trunk/.repoproject.list and manifests.git/config.