Use Pythonic way of calling esptool, avoid fork(#5797)

Simply import the pyserial and esptool modules directly into upload.py
instead of trying to fake things with os.fork()s.  Reduces code and is
more Pythonic.

Author: earlephilhower

package/package_esp8266com_index.template.json

@@ -137,17 +137,17 @@
                "systems": [
                   {
                      "host": "x86_64-mingw32",
-                     "url": "https://github.com/earlephilhower/esp-quick-toolchain/releases/download/2.5.0-3/python-3.7.2.post1-embed-win32.zip",
-                     "archiveFileName": "python-3.7.2.post1-embed-win32.zip",
-                     "checksum": "SHA-256:8136937ac00c28549893d1241011054a0e90517e0a193c2986323fa9f6501ed9",
-                     "size": "6612720"
+                     "url": "https://github.com/earlephilhower/esp-quick-toolchain/releases/download/2.5.0-3/python-3.7.2.post1-embed-win32v2.zip",
+                     "archiveFileName": "python-3.7.2.post1-embed-win32v2.zip",
+                     "checksum": "SHA-256:26665d2925ee75118bb7d8620e9ee988adc2ca3e660a9f4c06a09a06c94c0c29",
+                     "size": "6431781"
                   },
                   {
                      "host": "i686-mingw32",
-                     "url": "https://github.com/earlephilhower/esp-quick-toolchain/releases/download/2.5.0-3/python-3.7.2.post1-embed-win32.zip",
-                     "archiveFileName": "python-3.7.2.post1-embed-win32.zip",
-                     "checksum": "SHA-256:8136937ac00c28549893d1241011054a0e90517e0a193c2986323fa9f6501ed9",
-                     "size": "6612720"
+                     "url": "https://github.com/earlephilhower/esp-quick-toolchain/releases/download/2.5.0-3/python-3.7.2.post1-embed-win32v2.zip",
+                     "archiveFileName": "python-3.7.2.post1-embed-win32v2.zip",
+                     "checksum": "SHA-256:26665d2925ee75118bb7d8620e9ee988adc2ca3e660a9f4c06a09a06c94c0c29",
+                     "size": "6431781"
                   }
                ]
             },

platform.txt

@@ -137,8 +137,7 @@ tools.esptool.upload.params.quiet=
 # First, potentially perform an erase or nothing
 # Next, do the binary upload
 # Combined in one rule because Arduino doesn't suport upload.1.pattern/upload.3.pattern
-tools.esptool.upload.pattern="{cmd}" "{runtime.platform.path}/tools/upload.py" "{runtime.platform.path}/tools/pyserial" "{runtime.platform.path}/tools/esptool/esptool.py" --chip esp8266 --port "{serial.port}" --baud "{upload.speed}" "{upload.verbose}" {upload.erase_cmd} --end  --chip esp8266 --port "{serial.port}" --baud "{upload.speed}" "{upload.verbose}" write_flash 0x0 "{build.path}/{build.project_name}.bin" --end
-
+tools.esptool.upload.pattern="{cmd}" "{runtime.platform.path}/tools/upload.py" "{runtime.platform.path}/tools/pyserial" "{runtime.platform.path}/tools/esptool" --chip esp8266 --port "{serial.port}" --baud "{upload.speed}" "{upload.verbose}" {upload.erase_cmd} --end  --chip esp8266 --port "{serial.port}" --baud "{upload.speed}" "{upload.verbose}" write_flash 0x0 "{build.path}/{build.project_name}.bin" --end
 
 tools.esptool.upload.network_pattern="{network_cmd}" "{runtime.platform.path}/tools/espota.py" -i "{serial.port}" -p "{network.port}" "--auth={network.password}" -f "{build.path}/{build.project_name}.bin"
 

tools/upload.py

@@ -3,32 +3,24 @@
 # Wrapper for Arduino core / others that can call esptool.py possibly multiple times
 # Adds pyserial to sys.path automatically based on the path of the current file
 
-# First patameter is pyserial path, then a series of command arguments separated with --end
-# i.e. upload.py tools/pyserial tools/esptool/esptool.py erase_flash --end write_flash file 0x0 --end
+# First parameter is pyserial path, second is esptool path, then a series of command arguments separated with --end
+# i.e. upload.py tools/pyserial tools/esptool erase_flash --end write_flash file 0x0 --end
 
-import inspect
-import os
 import sys
 
 sys.argv.pop(0) # Remove executable name
 try:
     sys.path.append(sys.argv.pop(0).replace('\\', '/')) # Add pyserial dir to search path, in UNIX format
-    esptool = sys.argv.pop(0).replace('\\', '/') # Full path to esptool.py, in UNIX format
+    sys.path.append(sys.argv.pop(0).replace('\\', '/')) # Add esptool dir to search path, in UNIX format
+    import esptool # If this fails, we can't continue and will bomb below
 except:
     sys.stderr.write("Error in command line, need pyserial path as 1st arg and esptool path as 2nd.\n")
     sys.exit(1)
 
 fakeargs = [];
 while len(sys.argv):
     if sys.argv[0] == '--end':
-        pid  = os.fork()
-        if pid == 0:
-            sys.argv = ['esptool.py'] + fakeargs
-            sys.stderr.write("Running: " + " ".join(sys.argv) + "\n")
-            exec(open(esptool).read())
-            sys.exit(0)
-        else:
-            os.waitpid(pid, 0)
+        esptool.main(fakeargs)
         sys.argv.pop(0) # Remove --end
         fakeargs = []
     else: