Fixed test compile-build on very long paths on Windows

Author: cmaglie

Diff for: test/conftest.py

@@ -20,6 +20,7 @@
 import simplejson as json
 from invoke import Local
 from invoke.context import Context
+import tempfile
 
 from .common import Board
 
@@ -31,7 +32,28 @@ def data_dir(tmpdir_factory):
     each test and deleted at the end, this way all the
     tests work in isolation.
     """
-    return str(tmpdir_factory.mktemp("ArduinoTest"))
+
+    # it seems that paths generated by pytest's tmpdir_factory are too
+    # long and may lead to arduino-cli compile failures due to the
+    # combination of (some or all of) the following reasons:
+    # 1) Windows not liking path >260 chars in len
+    # 2) arm-gcc not fully optimizing long paths
+    # 3) libraries requiring headers deep down the include path
+    # for example:
+    #
+    #             from C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\A7\packages\arduino\hardware\mbed\1.1.4\cores\arduino/mbed/rtos/Thread.h:29,
+    #             from C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\A7\packages\arduino\hardware\mbed\1.1.4\cores\arduino/mbed/rtos/rtos.h:28,
+    #             from C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\A7\packages\arduino\hardware\mbed\1.1.4\cores\arduino/mbed/mbed.h:23,
+    #             from C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\A7\packages\arduino\hardware\mbed\1.1.4\cores\arduino/Arduino.h:32,
+    #             from C:\Users\RUNNER~1\AppData\Local\Temp\arduino-sketch-739B2B6DD21EB014317DA2A46062811B\sketch\magic_wand.ino.cpp:1:
+    ##[error]c:\users\runneradmin\appdata\local\temp\pytest-of-runneradmin\pytest-0\a7\packages\arduino\tools\arm-none-eabi-gcc\7-2017q4\arm-none-eabi\include\c++\7.2.1\new:39:10: fatal error: bits/c++config.h: No such file or directory
+    #
+    # due to the above on Windows we cut the tmp path straight to /tmp/xxxxxxxx
+    if platform.system() == "Windows":
+        with tempfile.TemporaryDirectory() as tmp:
+            yield tmp
+    else:
+        yield str(tmpdir_factory.mktemp("ArduinoTest"))
 
 
 @pytest.fixture(scope="session")