[PATCH kvmtool 3/6] Makefile: support -s switch

[Andre Przywara <andre.przywara@arm.com>]

"make -s" suppresses normal output, just shows warnings and errors.
But since we explicitly override the make output with our fancy concise
version, we miss out on this feature.

Do as the kernel does and explicitly suppress every normal output when -s
is given. This helps to spot warnings that scroll out of the terminal
window too quickly.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
---
 Makefile | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index c4faff66..a68cfcd5 100644
--- a/Makefile
+++ b/Makefile
@@ -2,8 +2,22 @@
 # Define WERROR=0 to disable -Werror.
 #
 
+ifneq ($(filter 4.%,$(MAKE_VERSION)),)  # make-4
+ifneq ($(filter %s ,$(firstword x$(MAKEFLAGS))),)
+  silent=1
+endif
+else                                    # make-3.8x
+ifneq ($(filter s% -s%,$(MAKEFLAGS)),)
+  silent=1
+endif
+endif
+
 ifeq ($(strip $(V)),)
-	E = @echo
+	ifeq ($(silent),)
+		E = @echo
+	else
+		E = @\#
+	endif
 	Q = @
 else
 	E = @\#
-- 
2.17.1