configure: Print a more helpful error if autoconf-archive is not installed

... because an undefined macro receives another macro as parameter and
autoconf is not smart enough to produce a useful error message.

Signed-off-by: Radoslav Kolev <radoslav.kolev@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Author: radolin

configure.ac

@@ -1792,6 +1792,11 @@ LIBS=""
 # Defined in acinclude.m4.
 grub_ASM_USCORE
 grub_PROG_TARGET_CC
+
+# The error message produced by autoconf if autoconf-archive is not installed is
+# quite misleading and not very helpful. So, try point people in the right direction.
+m4_ifndef([AX_CHECK_LINK_FLAG], [m4_fatal([autoconf-archive is missing. You must install it to generate the configure script.])])
+
 if test "x$TARGET_APPLE_LINKER" != x1 ; then
 AX_CHECK_LINK_FLAG([-Wl,--image-base,0x400000],
     [TARGET_IMG_BASE_LDOPT="-Wl,--image-base"],