Created attachment 448690 [details] build log It seems that with curl linked against dev-libs/libressl-2.5.0 it is necessary to pass "-lssl" when linking against libcurl. For dev-vcs/git this leads to linking failures as illustrated in the attached build log. upstream git properly detects whether "-lssl" is needed, but the ebuild does not use the upstream configure script. (Why??) With NEEDS_SSL_WITH_CURL added to the make opts, the package compiles fine.
I can confirm that git-2.14.2 USE=curl compiles just fine with libressl-2.6.2 and curl-7.55.1. All of these versions are in portage, so I believe the bug can be closed now.
I cannot reproduce this any more. This was probably caused by a miscompiled libcurl. Closing as Invalid.