Requires:
This is a comma-separated list of packages that are required by your
package. Flags from dependent packages will be merged in to the
flags reported for your package. [...]
[...]
Libs:
This line should give the link flags specific to your package. Don't
add any flags for required packages; pkg-config will add those
automatically.
From https://linux.die.net/man/1/pkg-config:
Pull request pending...