Issue 49845 - Remove pkgconfig check for libasan
A recent commit introduced a pkgconfig check for libasan. However, ASAN
buildtime whereabouts are provided within compiler itself, hence there is no
external libasan.pc file, only dynamic linking to libasan is necessary.
Remove the superfluous check from configure.ac.
Author: Matus Honek <email@example.com>
Review by: ???
(cherry picked from commit 031c0b9defe7f79f55a9d9761062892daad227b5)