libicudata in non-standard directory linking issues.

Having had trouble getting icu compiled on Solaris with GCC, I
compiled it out of tree and placed it in /opt/icu on my computer (I
want to know what specifically needs to attach to non-standard
libraries on my system for portability)

however I noticed that although LibreOffice is happy to know it exists
it seems to go out of it's way not to try and include it in any paths
(LD_LIBRARY or CFLAGS).

whilst I can hack config_host.mk to make sure that it includes
"-I/opt/icu/include" and set my LD_LIBRARY_PATH so that it includes
the /opt/icu/lib, I have an issue with compiling tail_build on certain
modules because they redefine the LD)LIBRARY_PATH:

S=/home/sal/LibreOffice/libo && O=$S/solver/unxsogi &&
W=$S/workdir/unxsogi &&  LD_LIBRARY_PATH="$O/lib" $O/bin/gencoll_rule
$S/i18npool/source/collator/data/ja_charset.txt
$W/CustomTarget/i18npool/collator/collator_ja_charset.cxx ja_charset
ld.so.1: gencoll_rule: fatal: libicudata.so.40: open failed: No such
file or directory
gmake: *** 
[/home/sal/LibreOffice/libo/workdir/unxsogi/CustomTarget/i18npool/collator/collator_ja_charset.cxx]
Killed

can anyone tell me where this is defined in the source code, and how
to tell it to go away, or how to tell the system to include the ICU
path given to it via icu-config?

Thanks in advance.

Jon