[PATCH v4 6/9] Makefile: move $(comma), $(empty) and $(space) to shared.mak

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Move these variables over to the shared.mak, we'll make use of them in
a subsequent commit.

Note that there's reason for these to be "simply expanded variables",
i.e. to use ":=" assignments instead of lazily expanded "="
assignments. We could use "=", but let's leave this as-is for now for
ease of review.

See 425ca6710b2 (Makefile: allow combining UBSan with other
sanitizers, 2017-07-15) for the commit that introduced these.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Makefile   | 4 ----
 shared.mak | 8 ++++++++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Makefile b/Makefile
index ce362720947..1e7a1277ce9 100644
--- a/Makefile
+++ b/Makefile
@@ -1289,10 +1289,6 @@ endif
 ALL_CFLAGS = $(DEVELOPER_CFLAGS) $(CPPFLAGS) $(CFLAGS)
 ALL_LDFLAGS = $(LDFLAGS)
 
-comma := ,
-empty :=
-space := $(empty) $(empty)
-
 ifdef SANITIZE
 SANITIZERS := $(foreach flag,$(subst $(comma),$(space),$(SANITIZE)),$(flag))
 BASIC_CFLAGS += -fsanitize=$(SANITIZE) -fno-sanitize-recover=$(SANITIZE)
diff --git a/shared.mak b/shared.mak
index 1dda948df09..934bf428936 100644
--- a/shared.mak
+++ b/shared.mak
@@ -23,3 +23,11 @@
 #
 #    info make --index-search=.DELETE_ON_ERROR
 .DELETE_ON_ERROR:
+
+### Global variables
+
+## comma, empty, space: handy variables as these tokens are either
+## special or can be hard to spot among other Makefile syntax.
+comma := ,
+empty :=
+space := $(empty) $(empty)
-- 
2.35.1.1228.g56895c6ee86