Log Message:
Due to directory style layout change, Haiku's SYSLIBPATH may not be
/boot/common/lib.
Undef it for Haiku and COMPILER_LIB_DIRS instead (also for other platforms
not set here).
XXX: all platforms should be SYSLIBPATH=${COMPILER_LIB_DIRS}, or
XXX: _OPSYS_LIB_DIRS for such platforms should be fixed.