PKG_PROG_PKG_CONFIG checks the version of pkg-config on the user's system at build time. What is not available is a way to check the version of pkg.m4 at autogen time. This would allow developers to specify a version that contains a new macro or a version where a bug in a macro was fixed. I'm leaning towards adding PKG_PREREQ like AC_PREREQ or LT_PREREQ where you can specify this version. I'd just use the same package version as pkg-config itself and substitute it into pkg.m4 at pkg-config build time.
Fixed in commit b51cd216.
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.