buildsys: touch incremental-lint in check target to avoid triggering twice

Without this the check and the, through the 'install' target
triggered, incremental lint target triggered a full eslint run.

Makes it similar to what PBS did from the beginning of eslint
inclusion..

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/Makefile

@@ -88,6 +88,7 @@ all: ${SUBDIRS}
 check: lint
 lint: ${JSSRC}
 	eslint --strict ${JSSRC}
+	touch ".lint-incremental"
 
 proxmoxlib.js: .lint-incremental ${JSSRC}
 	# add the version as comment in the file