glibc: ensure BR2_MAKE is also used for subdirs

The configure script contains logic to figure out what make program to
invoke for subdirectories (trying gnumake, gmake, make).  Explicitly force
it to use our BR2_MAKE to ensure the right make version is used.

As GLIBC_CONF_ENV is only initialized below, move this section below it.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/glibc/glibc.mk

@@ -31,10 +31,6 @@ GLIBC_ADD_TOOLCHAIN_DEPENDENCY = NO
 GLIBC_DEPENDENCIES = host-gcc-initial linux-headers host-bison host-gawk \
 	$(BR2_MAKE_HOST_DEPENDENCY)
 
-# glibc requires make >= 4.0 since 2.28 release.
-# https://www.sourceware.org/ml/libc-alpha/2018-08/msg00003.html
-GLIBC_MAKE = $(BR2_MAKE)
-
 GLIBC_SUBDIR = build
 
 GLIBC_INSTALL_STAGING = YES
@@ -82,6 +78,11 @@ ifeq ($(BR2_riscv),y)
 GLIBC_CONF_ENV += libc_cv_slibdir=/lib64 libc_cv_rtlddir=/lib
 endif
 
+# glibc requires make >= 4.0 since 2.28 release.
+# https://www.sourceware.org/ml/libc-alpha/2018-08/msg00003.html
+GLIBC_MAKE = $(BR2_MAKE)
+GLIBC_CONF_ENV += ac_cv_prog_MAKE="$(BR2_MAKE)"
+
 # Even though we use the autotools-package infrastructure, we have to
 # override the default configure commands for several reasons:
 #