Recognize MSYS(MINGW) as Windows for toolchain get (#7358)

Add the ID string reported by MSYS's latest tools under Windows with
the string "MINGW..." as "Windows" for toolchain selection in get.py

Author: earlephilhower

tools/get.py

@@ -113,6 +113,8 @@ def identify_platform():
         sys_name = 'Windows'
     if 'MSYS_NT' in sys_name:
         sys_name = 'Windows'
+    if 'MINGW' in sys_name:
+        sys_name = 'Windows'
     return arduino_platform_names[sys_name][bits]
 
 def main():