scalar Makefile: use "The default target of..." pattern

Make the "contrib/scalar/Makefile" be stylistically consistent with
the top-level "Makefile" in first declaring "all" to be the default
rule, followed by including other Makefile snippets.

This adjusts code added in 0a43fb2 (scalar: create a rudimentary
executable, 2021-12-03), it further ensures that when we add another
"include" file in a subsequent commit that the included file won't be
the one to define our default target.

Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

contrib/scalar/Makefile

@@ -1,3 +1,10 @@
+# The default target of this Makefile is...
+all::
+
+include ../../config.mak.uname
+-include ../../config.mak.autogen
+-include ../../config.mak
+
 QUIET_SUBDIR0  = +$(MAKE) -C # space to separate -C and subdir
 QUIET_SUBDIR1  =
 
@@ -12,12 +19,6 @@ else
 endif
 endif
 
-all:
-
-include ../../config.mak.uname
--include ../../config.mak.autogen
--include ../../config.mak
-
 TARGETS = scalar$(X) scalar.o
 GITLIBS = ../../common-main.o ../../libgit.a ../../xdiff/lib.a