kbuild: do not generate .tmp_vmlinux*.map when CONFIG_VMLINUX_MAP=y

Commit 5cc124720461 ("kbuild: add CONFIG_VMLINUX_MAP expert option")
mentioned that "the .map file can be rather large (several MB), and
that's a waste of space when one isn't interested in these things."

If that is the case, generating map files for the intermediate
tmp_vmlinux* files is also a waste of space. It is unlikely that
anyone would be interested in the .tmp_vmlinux*.map files.

This commit stops passing the -Map= option when linking the .tmp_vmlinux*
intermediates.

I also hard-coded the file name 'vmlinux.map' instead of ${output}.map
because a later commit will introduce vmlinux.unstripped but I want to
keep the current name of the map file.

Signed-off-by: Masahiro Yamada <[e-mail]>
Acked-by: Ard Biesheuvel <[e-mail]>

scripts/link-vmlinux.sh

···
 		ldflags="${ldflags} ${wl}--strip-debug"
 	fi
 
-	if is_enabled CONFIG_VMLINUX_MAP; then
-		ldflags="${ldflags} ${wl}-Map=${output}.map"
+	if [ -n "${generate_map}" ];  then
+		ldflags="${ldflags} ${wl}-Map=vmlinux.map"
 	fi
 
 	${ld} ${ldflags} -o ${output}					\
···
 btf_vmlinux_bin_o=
 kallsymso=
 strip_debug=
+generate_map=
 
 if is_enabled CONFIG_KALLSYMS; then
 	true > .tmp_vmlinux0.syms
···
 fi
 
 strip_debug=
+
+if is_enabled CONFIG_VMLINUX_MAP; then
+	generate_map=1
+fi
 
 vmlinux_link vmlinux