If $PKG_CONFIG contains a space, then the test may not work, so
surround with quotation mark characters. (for example,
PKG_CONFIG="pkg-config --static" breaks configure before this commit).
Silences notice on newer autoconf:
libtoolize: Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
libtoolize: rerunning libtoolize, to keep the correct libtool macros in-tree.
This helps keep the top-level build directory clean, too
