Makefile: do not install sourced rebase scripts

When git-rebase.sh recently started sourcing
git-rebase--interactive.sh instead of executing it, executable bit of
the latter file should have been turned off and it should have been
moved from SCRIPT_SH to SCRIPT_LIB in the Makefile. Its two new
siblings, git-rebase--am.sh and git-rebase--merge.sh (whose executable
bits are already off) should also be moved to SCRIPT_LIB in the
Makefile.
Reported-by: NJohannes Sixt <j6t@kdbg.org>
Helped-by: NJeff King <peff@peff.net>
Signed-off-by: NMartin von Zweigbergk <martin.von.zweigbergk@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -369,9 +369,6 @@ SCRIPT_SH += git-merge-resolve.sh
 SCRIPT_SH += git-mergetool.sh
 SCRIPT_SH += git-pull.sh
 SCRIPT_SH += git-quiltimport.sh
-SCRIPT_SH += git-rebase--am.sh
-SCRIPT_SH += git-rebase--interactive.sh
-SCRIPT_SH += git-rebase--merge.sh
 SCRIPT_SH += git-rebase.sh
 SCRIPT_SH += git-repack.sh
 SCRIPT_SH += git-request-pull.sh
@@ -381,6 +378,9 @@ SCRIPT_SH += git-web--browse.sh
 
 SCRIPT_LIB += git-mergetool--lib
 SCRIPT_LIB += git-parse-remote
+SCRIPT_LIB += git-rebase--am
+SCRIPT_LIB += git-rebase--interactive
+SCRIPT_LIB += git-rebase--merge
 SCRIPT_LIB += git-sh-setup
 
 SCRIPT_PERL += git-add--interactive.perl