Cygwin build not to use -fPIC
Cygwin build not to use -fPIC

Summary:
Cygwin doesn't support -fPIC. Remove it.
Not sure whether we can build shared library in Cygwin but at least it can build without warning.

Test Plan: Build under Cygwin

Reviewers: yhchiang, rven, kradhakrishnan, igor

Reviewed By: igor

Subscribers: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D40077

temicai/rocksdb,caijieming-baidu/rocksdb,makelivedotnet/rocksdb,vmx/rocksdb,tsheasha/rocksdb,sorphi/rocksdb,JackLian/rocksdb,Vaisman/rocksdb,wenduo/rocksdb,IMCG/RcoksDB,sorphi/rocksdb,ryneli/rocksdb,mbarbon/rocksdb,alihalabyah/rocksdb,jalexanderqed/rocksdb,wskplho/rocksdb,anagav/rocksdb,alihalabyah/rocksdb,skunkwerks/rocksdb,SunguckLee/RocksDB,makelivedotnet/rocksdb,tsheasha/rocksdb,luckywhu/rocksdb,lgscofield/rocksdb,tizzybec/rocksdb,tizzybec/rocksdb,vmx/rocksdb,ryneli/rocksdb,lgscofield/rocksdb,vmx/rocksdb,JohnPJenkins/rocksdb,OverlordQ/rocksdb,Andymic/rocksdb,tizzybec/rocksdb,geraldoandradee/rocksdb,bbiao/rocksdb,wlqGit/rocksdb,biddyweb/rocksdb,luckywhu/rocksdb,RyanTech/rocksdb,skunkwerks/rocksdb,jalexanderqed/rocksdb,bbiao/rocksdb,Applied-Duality/rocksdb,makelivedotnet/rocksdb,zhangpng/rocksdb,wlqGit/rocksdb,IMCG/RcoksDB,sorphi/rocksdb,bbiao/rocksdb,vmx/rocksdb,tsheasha/rocksdb,JackLian/rocksdb,vashstorm/rocksdb,IMCG/RcoksDB,facebook/rocksdb,JackLian/rocksdb,Vaisman/rocksdb,Vaisman/rocksdb,biddyweb/rocksdb,lgscofield/rocksdb,wlqGit/rocksdb,ylong/rocksdb,JohnPJenkins/rocksdb,Andymic/rocksdb,ryneli/rocksdb,wskplho/rocksdb,temicai/rocksdb,Andymic/rocksdb,JohnPJenkins/rocksdb,temicai/rocksdb,kaschaeffer/rocksdb,JoeWoo/rocksdb,hobinyoon/rocksdb,RyanTech/rocksdb,vashstorm/rocksdb,JackLian/rocksdb,tsheasha/rocksdb,biddyweb/rocksdb,JoeWoo/rocksdb,OverlordQ/rocksdb,alihalabyah/rocksdb,geraldoandradee/rocksdb,biddyweb/rocksdb,siddhartharay007/rocksdb,sorphi/rocksdb,sorphi/rocksdb,fengshao0907/rocksdb,kaschaeffer/rocksdb,norton/rocksdb,wenduo/rocksdb,Applied-Duality/rocksdb,flabby/rocksdb,wlqGit/rocksdb,hobinyoon/rocksdb,rDSN-Projects/rocksdb.replicated,ylong/rocksdb,ylong/rocksdb,OverlordQ/rocksdb,bbiao/rocksdb,flabby/rocksdb,caijieming-baidu/rocksdb,JackLian/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,temicai/rocksdb,wenduo/rocksdb,dkorolev/rocksdb,SunguckLee/RocksDB,hobinyoon/rocksdb,wlqGit/rocksdb,RyanTech/rocksdb,geraldoandradee/rocksdb,IMCG/RcoksDB,RyanTech/rocksdb,wskplho/rocksdb,Vaisman/rocksdb,norton/rocksdb,fengshao0907/rocksdb,dkorolev/rocksdb,OverlordQ/rocksdb,wat-ze-hex/rocksdb,caijieming-baidu/rocksdb,rDSN-Projects/rocksdb.replicated,skunkwerks/rocksdb,caijieming-baidu/rocksdb,luckywhu/rocksdb,rDSN-Projects/rocksdb.replicated,facebook/rocksdb,SunguckLee/RocksDB,ylong/rocksdb,kaschaeffer/rocksdb,RyanTech/rocksdb,luckywhu/rocksdb,OverlordQ/rocksdb,makelivedotnet/rocksdb,geraldoandradee/rocksdb,ryneli/rocksdb,flabby/rocksdb,jalexanderqed/rocksdb,IMCG/RcoksDB,bbiao/rocksdb,hobinyoon/rocksdb,bbiao/rocksdb,lgscofield/rocksdb,Andymic/rocksdb,mbarbon/rocksdb,dkorolev/rocksdb,luckywhu/rocksdb,JohnPJenkins/rocksdb,wskplho/rocksdb,zhangpng/rocksdb,temicai/rocksdb,sorphi/rocksdb,OverlordQ/rocksdb,anagav/rocksdb,wat-ze-hex/rocksdb,vashstorm/rocksdb,wenduo/rocksdb,RyanTech/rocksdb,siddhartharay007/rocksdb,makelivedotnet/rocksdb,wat-ze-hex/rocksdb,mbarbon/rocksdb,jalexanderqed/rocksdb,wenduo/rocksdb,hobinyoon/rocksdb,zhangpng/rocksdb,vashstorm/rocksdb,wskplho/rocksdb,lgscofield/rocksdb,skunkwerks/rocksdb,siddhartharay007/rocksdb,vmx/rocksdb,dkorolev/rocksdb,kaschaeffer/rocksdb,flabby/rocksdb,makelivedotnet/rocksdb,OverlordQ/rocksdb,anagav/rocksdb,fengshao0907/rocksdb,temicai/rocksdb,JohnPJenkins/rocksdb,mbarbon/rocksdb,biddyweb/rocksdb,anagav/rocksdb,facebook/rocksdb,Vaisman/rocksdb,hobinyoon/rocksdb,facebook/rocksdb,norton/rocksdb,zhangpng/rocksdb,ylong/rocksdb,lgscofield/rocksdb,Applied-Duality/rocksdb,wenduo/rocksdb,fengshao0907/rocksdb,tsheasha/rocksdb,wat-ze-hex/rocksdb,siddhartharay007/rocksdb,vashstorm/rocksdb,vmx/rocksdb,wskplho/rocksdb,sorphi/rocksdb,SunguckLee/RocksDB,JoeWoo/rocksdb,alihalabyah/rocksdb,Applied-Duality/rocksdb,tsheasha/rocksdb,lgscofield/rocksdb,wskplho/rocksdb,jalexanderqed/rocksdb,flabby/rocksdb,tizzybec/rocksdb,ylong/rocksdb,caijieming-baidu/rocksdb,biddyweb/rocksdb,caijieming-baidu/rocksdb,wat-ze-hex/rocksdb,makelivedotnet/rocksdb,geraldoandradee/rocksdb,dkorolev/rocksdb,JohnPJenkins/rocksdb,jalexanderqed/rocksdb,skunkwerks/rocksdb,skunkwerks/rocksdb,facebook/rocksdb,mbarbon/rocksdb,vmx/rocksdb,geraldoandradee/rocksdb,skunkwerks/rocksdb,jalexanderqed/rocksdb,JackLian/rocksdb,kaschaeffer/rocksdb,ryneli/rocksdb,flabby/rocksdb,temicai/rocksdb,facebook/rocksdb,IMCG/RcoksDB,JohnPJenkins/rocksdb,siddhartharay007/rocksdb,flabby/rocksdb,Vaisman/rocksdb,hobinyoon/rocksdb,wlqGit/rocksdb,JoeWoo/rocksdb,luckywhu/rocksdb,RyanTech/rocksdb,fengshao0907/rocksdb,Andymic/rocksdb,norton/rocksdb,geraldoandradee/rocksdb,Applied-Duality/rocksdb,JoeWoo/rocksdb,biddyweb/rocksdb,rDSN-Projects/rocksdb.replicated,norton/rocksdb,dkorolev/rocksdb,facebook/rocksdb,anagav/rocksdb,Applied-Duality/rocksdb,zhangpng/rocksdb,ryneli/rocksdb,luckywhu/rocksdb,tsheasha/rocksdb,Andymic/rocksdb,tizzybec/rocksdb,wenduo/rocksdb,siddhartharay007/rocksdb,Applied-Duality/rocksdb,hobinyoon/rocksdb,alihalabyah/rocksdb,SunguckLee/RocksDB,tizzybec/rocksdb,ylong/rocksdb,rDSN-Projects/rocksdb.replicated,Andymic/rocksdb,mbarbon/rocksdb,wenduo/rocksdb,kaschaeffer/rocksdb,siddhartharay007/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,vmx/rocksdb,SunguckLee/RocksDB,alihalabyah/rocksdb,zhangpng/rocksdb,caijieming-baidu/rocksdb,Vaisman/rocksdb,tsheasha/rocksdb,anagav/rocksdb,wat-ze-hex/rocksdb,rDSN-Projects/rocksdb.replicated,vashstorm/rocksdb,norton/rocksdb,Andymic/rocksdb,wat-ze-hex/rocksdb,mbarbon/rocksdb,JackLian/rocksdb,facebook/rocksdb,ryneli/rocksdb,JoeWoo/rocksdb,zhangpng/rocksdb,tizzybec/rocksdb,fengshao0907/rocksdb,SunguckLee/RocksDB,dkorolev/rocksdb,JoeWoo/rocksdb,IMCG/RcoksDB,rDSN-Projects/rocksdb.replicated,wlqGit/rocksdb,alihalabyah/rocksdb,norton/rocksdb,kaschaeffer/rocksdb,norton/rocksdb,anagav/rocksdb,vashstorm/rocksdb,fengshao0907/rocksdb