Change hardcoded path to tzdata directory

[Thomas Mader]

Hello,

I added the TZ_DATABASE_DIR option to the Phobos Makefile to 
change the hardcoded path in the code with 
https://github.com/dlang/phobos/pull/5966.
Is LDC using this Makefile to build Phobos and is it possible to 
specify that option in the LDC build somehow or do I need to 
implement a solution for LDC too?

Thomas