support/gnuconfig: bump version

Build with uclinux-uclibc toolchains are broken since commit
cf8162ce51 so bump version to get
https://git.savannah.gnu.org/cgit/config.git/commit/?id=d7a4dee7cc25e332b990d0a6d9f0ddd42cb33cf5

Fixes:
 - http://autobuild.buildroot.org/results/f8528d568de0dad751129900ae38ae292d7567b9

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

support/gnuconfig/README.buildroot

@@ -18,4 +18,4 @@ Run the script 'update' in this directory, and commit the result.
 The current Buildroot version is based on this commit of the config.git
 repository (leave alone on its own line, the script updates it):
 
-e072cc210e5d0584396f6c13ba34cb9c7bd8538d
+d7a4dee7cc25e332b990d0a6d9f0ddd42cb33cf5

support/gnuconfig/config.guess

@@ -2,7 +2,7 @@
 # Attempt to guess a canonical system name.
 #   Copyright 1992-2020 Free Software Foundation, Inc.
 
-timestamp='2020-08-17'
+timestamp='2020-09-19'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -150,17 +150,15 @@ Linux|GNU|GNU/*)
 	#elif defined(__dietlibc__)
 	LIBC=dietlibc
 	#else
+	#include <stdarg.h>
+	#ifdef __DEFINED_va_list
+	LIBC=musl
+	#else
 	LIBC=gnu
 	#endif
+	#endif
 	EOF
 	eval "`$CC_FOR_BUILD -E "$dummy.c" 2>/dev/null | grep '^LIBC' | sed 's, ,,g'`"
-
-	# If ldd exists, use it to detect musl libc.
-	if command -v ldd >/dev/null && \
-		ldd --version 2>&1 | grep -q ^musl
-	then
-	    LIBC=musl
-	fi
 	;;
 esac
 

support/gnuconfig/config.sub

@@ -1733,7 +1733,9 @@ esac
 # As a final step for OS-related things, validate the OS-kernel combination
 # (given a valid OS), if there is a kernel.
 case $kernel-$os in
-	linux-gnu* | linux-dietlibc* | linux-android* | linux-newlib* | linux-musl* | linux-uclibc* )
+	linux-gnu* | linux-dietlibc* | linux-android* | linux-newlib* | linux-musl* | linux-uclibc* | uclinux-gnu* | uclinux-uclibc* )
+		;;
+	uclinux-uclibc* )
 		;;
 	-dietlibc* | -newlib* | -musl* | -uclibc* )
 		# These are just libc implementations, not actual OSes, and thus