/usr/lib/x86_64-linux-gnu/pkgconfig/ostree-1.pc is in libostree-dev 2018.4-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 | prefix=/usr
exec_prefix=${prefix}
libdir=${prefix}/lib/x86_64-linux-gnu
includedir=${prefix}/include
features= libsoup gpgme libarchive selinux libmount release
Name: OSTree
Description: Git for operating system binaries
Version: 2018.4
Requires: gio-unix-2.0
Libs: -L${libdir} -lostree-1
Cflags: -I${includedir}/ostree-1
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