Fixed LDFLAGS for prefix installation of libev.
Fixed LDFLAGS for prefix installation of libev.

Review: https://reviews.apache.org/r/24733

gsantovena/mesos,Gilbert88/mesos,verizonlabs/mesos,yuquanshan/customizedMesos,neilconway/mesos,andschwa/mesos,zmalik/mesos,craimbert/mesos,yuquanshan/customizedMesos,neilconway/mesos,chhsia0/mesos,asamerh4/mesos,jpeach/mesos,jpeach/mesos,gsantovena/mesos,chhsia0/mesos,craimbert/mesos,craimbert/mesos,neilconway/mesos,reneploetz/mesos,gsantovena/mesos,abudnik/mesos,reneploetz/mesos,zmalik/mesos,kaysoky/mesos,asamerh4/mesos,abudnik/mesos,reneploetz/mesos,neilconway/mesos,zmalik/mesos,reneploetz/mesos,andschwa/mesos,reneploetz/mesos,chhsia0/mesos,asamerh4/mesos,verizonlabs/mesos,asamerh4/mesos,chhsia0/mesos,asamerh4/mesos,chhsia0/mesos,verizonlabs/mesos,kaysoky/mesos,zmalik/mesos,andschwa/mesos,dforsyth/mesos,chhsia0/mesos,zmalik/mesos,gsantovena/mesos,neilconway/mesos,craimbert/mesos,dforsyth/mesos,yuquanshan/customizedMesos,Aman-Jain-14/customizedMesos,craimbert/mesos,reneploetz/mesos,jpeach/mesos,jpeach/mesos,abudnik/mesos,verizonlabs/mesos,Gilbert88/mesos,kaysoky/mesos,Gilbert88/mesos,abudnik/mesos,dforsyth/mesos,andschwa/mesos,gsantovena/mesos,Aman-Jain-14/customizedMesos,dforsyth/mesos,andschwa/mesos,dforsyth/mesos,craimbert/mesos,Gilbert88/mesos,Gilbert88/mesos,kaysoky/mesos,jpeach/mesos,jpeach/mesos,gsantovena/mesos,yuquanshan/customizedMesos,abudnik/mesos,kaysoky/mesos,jpeach/mesos,asamerh4/mesos,andschwa/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,gsantovena/mesos,zmalik/mesos,andschwa/mesos,verizonlabs/mesos,neilconway/mesos,asamerh4/mesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos,yuquanshan/customizedMesos,Aman-Jain-14/customizedMesos,Gilbert88/mesos,dforsyth/mesos,yuquanshan/customizedMesos,kaysoky/mesos,zmalik/mesos,abudnik/mesos,dforsyth/mesos,craimbert/mesos,Aman-Jain-14/customizedMesos,yuquanshan/customizedMesos,kaysoky/mesos,Gilbert88/mesos,abudnik/mesos,neilconway/mesos,reneploetz/mesos,Aman-Jain-14/customizedMesos,verizonlabs/mesos