manage compile and link flags for libraries for arm64 architecture

 pkg-config is a system for managing library compile and link flags that
 works with automake and autoconf.
 .
 Increasingly libraries ship with ".pc" files that allow querying of the
 compiler and linker flags needed to use them through the pkg-config(1)
 program.
 .
 This is a dependency package providing cross pkg-config support for the
 arm64 architecture.