Per the discussion on https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/mongodb-dev/mavDwuo7Mvo/sBIpF_pKBwAJ.

We should document the following less common build gotchas:

• SERVER-30893, that on ARM you must either disable hardware CRC32, or specify +crc in CCFLAGS.
• SERVER-38389, that use of ccache may break the build due to an SCons bug, with the workaround of setting MAXLINELENGTH to a very high value.