Reproduction steps

Build libgit2 with mbedtls using the patch from #4173
Used this patch at https://anonscm.debian.org/git/collab-maint/libgit2.git/tree/debian/patches/use-mbedtls.patch

and build it in a clean chroot without openssl.

Expected behavior

It should not add openssl as a dependency in .pc.

Actual behavior

The generated ibgit2.pc has openssl

prefix="/usr"
libdir=${prefix}/lib/x86_64-linux-gnu
includedir=${prefix}/include

Name: libgit2
Description: The git library, take 2
Version: 0.27.0

Libs: -L${libdir} -lgit2
Libs.private: -lrt -lpthread -lhttp_parser -lssh2
Requires.private: openssl zlib

Cflags: -I${includedir}

and makes build of other software using libgit2 to fail. See
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=899036

Version of libgit2 (release number or SHA1)

0.27.0

Operating system(s) tested

Debian unstable/experimental.