/usr/lib/x86_64-linux-gnu/pkgconfig/fwup.pc is in libfwup-dev 8-3.
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 | prefix=/usr
exec_prefix=/usr
libdir=/usr/lib/x86_64-linux-gnu
includedir=/usr/include
Name: fwup
Description: Library for deployment of UEFI firmware updates.
Version: 8
Requires: efivar >= 28
Libs: -L${libdir} -lfwup
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