Fixed glibc to use extraconfopt instead of confopt, which get reseted after calling set_confopt

Note: If in doubt please use extraconfopt instead of confopt as extraconfopt's
      will be also available after calling set_confopt!

base/glibc/glibc.conf

@@ -37,7 +37,7 @@ if atstage toolchain; then
 
 	hook_add postmake 5 'pkg_glibc_postmake_headers'
 else
-	var_append confopt " " "--with-headers=$root/usr/include"
+	var_append extraconfopt " " "--with-headers=$root/usr/include"
 
 	if [ "$SDECFG_MULTILIB" == 1 ] ; then
 		# set the ABI for each buildloop
@@ -88,10 +88,10 @@ pkg_glibc_objdir(){
 }
 hook_add preconf 9 "pkg_glibc_objdir"
 
-var_append confopt " " "--with-gnu-binutils --build=${arch_build} --host=${arch_target}"
+var_append extraconfopt " " "--with-gnu-binutils --build=${arch_build} --host=${arch_target}"
 
 if pkginstalled libgd; then
-	var_append confopt " " "--with-gd=/usr --with-gd-lib=/usr/lib --with-gd-include=/usr/include"
+	var_append extraconfopt " " "--with-gd=/usr --with-gd-lib=/usr/lib --with-gd-include=/usr/include"
 fi
 
 # --enable-add-ons expects a comma seperated list of add-ons