/usr/lib/x86_64-linux-gnu/pkgconfig/nss.pc is in libnss3-dev 2:3.21-1ubuntu4.
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 | prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib/x86_64-linux-gnu
includedir=${prefix}/include/nss
Name: NSS
Description: Mozilla Network Security Services
Version: 3.21
Requires: nspr
Libs: -L${libdir} -lnss3 -lnssutil3 -lsmime3 -lssl3
Cflags: -I${includedir}
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