fix os_min_ver for noarch (followup for SynoCommunity#4219)

Author: hgy59

mk/spksrc.spk.mk

@@ -15,6 +15,8 @@ else
 SPK_ARCH = noarch
 SPK_NAME_ARCH = noarch
 SPK_TCVERS = all
+OS_MIN_VER = 3.1-1594
+FIRMWARE = $(OS_MIN_VER)
 endif
 
 SPK_FILE_NAME = $(PACKAGES_DIR)/$(SPK_NAME)_$(SPK_NAME_ARCH)-$(SPK_TCVERS)_$(SPK_VERS)-$(SPK_REV).spk