kernel: include modinfo for built-in modules

Add modules.builtin.modinfo to the kernel package, to support presence
testing using module aliases and printing module details with 'modinfo'.

With related kmodloader changes this adds ~2 KB to compressed image sizes.

     root@OpenWrt:/# modinfo unix
     name:           unix
     filename:       (builtin)
     alias:          net-pf-1
     license:        GPL

     root@OpenWrt:/# modprobe net-pf-1 && echo SUCCESS || echo FAIL
     SUCCESS

Signed-off-by: Tony Ambardar <[email protected]>

package/kernel/linux/Makefile

@@ -61,6 +61,9 @@ define Package/kernel/install
 	$(INSTALL_DIR) $(1)/$(MODULES_SUBDIR)
 	$(INSTALL_DATA) $(LINUX_DIR)/modules.builtin $(1)/$(MODULES_SUBDIR)
 	$(SED) 's,.*/,,' $(1)/$(MODULES_SUBDIR)/modules.builtin
+	strings $(LINUX_DIR)/modules.builtin.modinfo | \
+		grep -E -v "\.(file$(if CONFIG_MODULE_STRIPPED,|parmtype))=" | \
+		tr '\n' '\0' > $(1)/$(MODULES_SUBDIR)/modules.builtin.modinfo
 endef
 
 define Package/kernel/extra_provides