[build] question: build environment variable BUILD_SPECIAL

[Oliver-Rainer Wittmann]

Hi,

while working on issue 121388 [1] I stumbled over build environment variable 
BUILD_SPECIAL which is by default not set.

Before I do my own investigation I want to ask here, if somebody has already an 
overview about the stuff which is enabled/disabled by setting/unsetting this 
build environment variable.

[1] https://issues.apache.org/ooo/show_bug.cgi?id=121388

Thanks in advance, Oliver.