make: fix build with glibc 2.27

make: fix build with glibc 2.27

glibc 2.27 changed _GNU_GLOB_INTERFACE_VERSION to 2. This triggers build
of the internal glob implementation in make. This internal
implementation needs the __alloca symbol that glibc does not define.

Add upstream patch that adds support for _GNU_GLOB_INTERFACE_VERSION 2.

Add host-pkgconf dependency for the PKG_CHECK_MODULES macro. This macro
is only used for guile, which we currently disable unconditionally. So
host-pkgconf is only needed now so that autoreconf generates a valid
configure script.

Fixes:
http://autobuild.buildroot.net/results/8ff/8ff06ad8438cfcac85577b24675dd1d66f7d3d03/
http://autobuild.buildroot.net/results/5cc/5ccee6bb332e800e81052a3094746edde83403b1/
http://autobuild.buildroot.net/results/841/8418f5ed56dacd6900946e7d56ad36ad03c7bf7e/

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>