/usr/lib/x86_64-linux-gnu/pkgconfig/termkey.pc is in libtermkey-dev 0.19-1.
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 | libdir=/usr/lib/x86_64-linux-gnu
includedir=/usr/include
Name: termkey
Description: Abstract terminal key input library
Version: 0.19
Libs: -L${libdir} -ltermkey
Cflags: -I${includedir}
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