Make LD -r as macros that can be changed for QNX.

src/Makefile.shlib

src/backend/Makefile

src/backend/access/Makefile

src/backend/access/common/Makefile

src/backend/access/gist/Makefile

src/backend/access/hash/Makefile

src/backend/access/heap/Makefile

src/backend/access/index/Makefile

src/backend/access/nbtree/Makefile

src/backend/access/rtree/Makefile

src/backend/access/transam/Makefile

src/backend/bootstrap/Makefile

src/backend/catalog/Makefile

src/backend/commands/Makefile

src/backend/executor/Makefile

src/backend/lib/Makefile

src/backend/libpq/Makefile

src/backend/main/Makefile

src/backend/nodes/Makefile

src/backend/optimizer/Makefile