doc: Fix indentation in build options documentation
doc: Fix indentation in build options documentation

Sphinx was showing the following warning message:

docs/getting_started/build-options.rst:200: WARNING: Bullet list ends
without a blank line; unexpected unindent.

Change-Id: Iad5d49c1e0d25dd623ad15bce1af31babf860c03
Signed-off-by: Sandrine Bailleux <4b69fcfca8da45b0c11ecda5434c5da526575d9d@arm.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware