rules.mk: add INSTALL_SUID macro

This is useful for packages that want to stage SUID executables.

Signed-off-by: Jo-Philipp Wich <[email protected]>
(cherry picked from commit b0261ee5e9bcbc743960727b5aad1829250d1add)

rules.mk

@@ -265,6 +265,7 @@ PATCH:=patch
 PYTHON:=python
 
 INSTALL_BIN:=install -m0755
+INSTALL_SUID:install -m4755
 INSTALL_DIR:=install -d -m0755
 INSTALL_DATA:=install -m0644
 INSTALL_CONF:=install -m0600