I have found a type error in the chmod command execution introduced by the commit c1fa947ec08bd8783f6b2415dfe670e8701b09a1 (https://gitweb.gentoo.org/proj/crossdev.git/commit/wrappers/cross-pkg-config?id=c1fa947ec08bd8783f6b2415dfe670e8701b09a1). In particular chmod a+rx "{$pkg_config}" should be chmod a+rx "${pkg_config}"
thanks for pointing this out ! http://gitweb.gentoo.org/proj/crossdev.git/commit/?id=2cdf8714b2d575d6e1554b6ed397451b153ae76c