PostgreSQL10 beta2 with ICU - initdb fails on MacOS

Hi

On MacOS, I configured PG10 beta2 sources with '--with-icu" option along
with ICU_LIBS and ICU_CFLAGS env variables to define the location of the
ICU libs that I built. Once the staging is ready, I executed initdb but it
fails with the following error:
--
$./initdb -D /tmp/data
The files belonging to this database system will be owned by user
"buildfarm".
This user must also own the server process.

The database cluster will be initialized with locale "en_US.UTF-8".
The default database encoding has accordingly been set to "UTF8".
The default text search configuration will be set to "english".

Data page checksums are disabled.

creating directory /tmp/data ... ok
creating subdirectories ... ok
selecting default max_connections ... 100
selecting default shared_buffers ... 128MB
selecting dynamic shared memory implementation ... posix
creating configuration files ... ok
running bootstrap script ... ok
*performing post-bootstrap initialization ... 2017-07-12 11:18:21.187 BST
[53618] FATAL: could not open collator for locale "und":
U_FILE_ACCESS_ERROR*
*2017-07-12 11:18:21.187 BST [53618] STATEMENT: SELECT
pg_import_system_collations('pg_catalog');*
child process exited with exit code 1
initdb: removing data directory "/tmp/data"
--

Has anyone came across this? This error is not seen on Linux and Windows
though.

--
Sandeep Thakkar
EDB