init: use the correct path of the templates directory again

In df93e40 (init: refactor the template directory discovery into its
own function, 2024-03-29), I refactored the way the templates directory
is discovered.

The refactoring was faithful, but missed a reference in the `Makefile`
where the `DEFAULT_GIT_TEMPLATE_DIR` constant is defined. As a
consequence, Git v2.45.1 and friends will always use the hard-coded path
`/usr/share/git-core/templates`.

Let's fix that by defining the `DEFAULT_GIT_TEMPLATE_DIR` when building
`setup.o`, where that constant is actually used.

Signed-off-by: Johannes Schindelin <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: dscho

Makefile

@@ -2751,7 +2751,7 @@ exec-cmd.sp exec-cmd.s exec-cmd.o: EXTRA_CPPFLAGS = \
 	'-DFALLBACK_RUNTIME_PREFIX="$(prefix_SQ)"'
 
 builtin/init-db.sp builtin/init-db.s builtin/init-db.o: GIT-PREFIX
-builtin/init-db.sp builtin/init-db.s builtin/init-db.o: EXTRA_CPPFLAGS = \
+setup.sp setup.s setup.o: EXTRA_CPPFLAGS = \
 	-DDEFAULT_GIT_TEMPLATE_DIR='"$(template_dir_SQ)"'
 
 config.sp config.s config.o: GIT-PREFIX