Makefile: Add vendor SDK 2.1.0-18-g61248df.

Since 2.1.0 zip release, the way of SDK distribution switched to git repo
with binary blobs and stuff. The repo isn't tagged properly for releases,
so above "git describe --tags" output is used.

This SDK version contains alleged fix for KRACK vulnerability.

Makefile

@@ -23,6 +23,7 @@ UNZIP = unzip -q -o
 VENDOR_SDK_ZIP = $(VENDOR_SDK_ZIP_$(VENDOR_SDK))
 VENDOR_SDK_DIR = $(VENDOR_SDK_DIR_$(VENDOR_SDK))
 
+VENDOR_SDK_DIR_2.1.0-18-g61248df = ESP8266_NONOS_SDK-2.1.0-18-g61248df
 VENDOR_SDK_ZIP_2.1.0 = ESP8266_NONOS_SDK-2.1.0.zip
 VENDOR_SDK_DIR_2.1.0 = ESP8266_NONOS_SDK-2.1.0
 VENDOR_SDK_ZIP_2.0.0 = ESP8266_NONOS_SDK_V2.0.0_16_08_10.zip
@@ -179,6 +180,12 @@ $(VENDOR_SDK_DIR)/.dir: $(VENDOR_SDK_ZIP)
 	-mv License $(VENDOR_SDK_DIR)
 	touch $@
 
+$(VENDOR_SDK_DIR_2.1.0-18-g61248df)/.dir:
+	echo $(VENDOR_SDK_DIR_2.1.0-18-g61248df)
+	git clone https://github.com/espressif/ESP8266_NONOS_SDK $(VENDOR_SDK_DIR_2.1.0-18-g61248df)
+	(cd $(VENDOR_SDK_DIR_2.1.0-18-g61248df); git co 61248df5f6)
+	touch $@
+
 $(VENDOR_SDK_DIR_2.1.0)/.dir: $(VENDOR_SDK_ZIP_2.1.0)
 	$(UNZIP) $^
 	touch $@
@@ -197,7 +204,7 @@ $(VENDOR_SDK_DIR_1.5.4)/.dir: $(VENDOR_SDK_ZIP_1.5.4)
 
 sdk_patch: $(VENDOR_SDK_DIR)/.dir .sdk_patch_$(VENDOR_SDK)
 
-.sdk_patch_2.1.0: user_rf_cal_sector_set.o
+.sdk_patch_2.1.0-18-g61248df .sdk_patch_2.1.0: user_rf_cal_sector_set.o
 	echo -e "#undef ESP_SDK_VERSION\n#define ESP_SDK_VERSION 020100" >>$(VENDOR_SDK_DIR)/include/esp_sdk_ver.h
 	$(PATCH) -d $(VENDOR_SDK_DIR) -p1 < c_types-c99_sdk_2.patch
 	cd $(VENDOR_SDK_DIR)/lib; mkdir -p tmp; cd tmp; $(TOOLCHAIN)/bin/xtensa-lx106-elf-ar x ../libcrypto.a; cd ..; $(TOOLCHAIN)/bin/xtensa-lx106-elf-ar rs libwpa.a tmp/*.o