Can't find icu-uc to build IMAP 3.0.0

I am trying to build Cyrus-IMAP 3.0.0 on RHEL6. I am getting the following build error:

checking for ICU... configure: error: Package requirements (icu-uc) were not met:

No package 'icu-uc' found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables ICU_CFLAGS
and ICU_LIBS to avoid the need to call pkg-config.
See the pkg-config man page for more details.

I have already installed libicu-devel. What other package do I need to install to get past this check?

$ uname -a
Linux email-dev.ornl.gov 2.6.32-696.el6.x86_64 #1 SMP Tue Feb 21 00:53:17 EST 2017 x86_64 x86_64 x86_64 GNU/Linux

I have attached the config.log file.

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