Summary: Previously, RocksDB's build scripts used relative pathnames like ./build_detect_platform. This can cause problems if the user uses CDPATH. Also, it just doesn't seem right to me.
Test Plan:
make clean
make -j32 check
Reviewers: MarkCallaghan, dhruba, kailiu
Reviewed By: kailiu
CC: leveldb
Differential Revision: https://reviews.facebook.net/D12459
Summary: As Aaron suggested, there are quite some problems with our Makefile and scripts. So in this diff I did some cleanup for them and revise some part of the scripts/makefile to help people better understand some mysterious parts.
Test Plan:
Ran make in several modes;
Ran the updated scripts.
Reviewers: dhruba, emayanke, akushner
Differential Revision: https://reviews.facebook.net/D12285
