Make upload.py compatible with existing FS upload

PR esp8266#6765 introduced an incompatibility with the existing Java uploaders
for SPIFFS and LittleFS,  breaking them because of the upload.py
parameter format change to support single stage erase/upload.

Add in patch to silently eat the single --end and to parse the write
address and filename properly as generated by calls from the plugins,
while retaining compatibility with the current IDE changes.

Author: earlephilhower

tools/upload.py

@@ -22,6 +22,7 @@
 
 cmdline = []
 write_option = ''
+write_addr = '0x0'
 erase_addr = ''
 erase_len = ''
 
@@ -45,6 +46,16 @@
         erase_len = sys.argv.pop(0)
         thisarg = ''
 
+    # Backwards compatibility with fs upload tools, eat --end
+    if thisarg == '--end':
+        thisarg = ''
+
+    # Backwards compatibility with fs upload tools, parse write_flash for later use
+    if thisarg == 'write_flash':
+        write_addr = sys.argv.pop(0)
+        binary = sys.argv.pop(0)
+        thisarg = ''
+
     if os.path.isfile(thisarg):
         binary = thisarg
         thisarg = ''
@@ -55,7 +66,7 @@
 cmdline = cmdline + ['write_flash']
 if len(write_option):
     cmdline = cmdline + [write_option]
-cmdline = cmdline + ['0x0', binary]
+cmdline = cmdline + [write_addr, binary]
 
 erase_file = ''
 if len(erase_addr):