[PATCH 2/4] Makefile: Require GNU make 3.82+

[Roman Bolshakov]

QEMU build fails with cryptic messages if make is too old:

  Makefile.ninja:2655: *** multiple target patterns.  Stop.

To avoid the confusion it's worth to fail the build right away and print
a friendly error message.

Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
---
 Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Makefile b/Makefile
index 8373ddccc9..45d688b87b 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,11 @@ ifneq ($(words $(subst :, ,$(CURDIR))), 1)
   $(error main directory cannot contain spaces nor colons)
 endif
 
+ifeq ($(filter undefine,$(value .FEATURES)),)
+$(error Unsupported Make version: $(MAKE_VERSION). \
+        Please use GNU Make 3.82 or above)
+endif
+
 # Always point to the root of the build tree (needs GNU make).
 BUILD_DIR=$(CURDIR)
 
-- 
2.28.0