[Grbl_Esp32 PR#652] Fixed incremental compilation by emitting a pio_machine.h file instea…

Fixed incremental compilation by emitting a pio_machine.h file instead of using the -D preprocessor option that breaks it.
The pio_machine.h file will be emitted in the machine folder. Because of that, I added it to the .gitignore.

NOTE: ONLY THE PYTHON SCRIPTS HAVE CHANGED! SH/PS1 is still the same for now.

Test results of build-all show that the first build is slow, and subsequent builds are much faster:

C:\devt\Grbl_Esp32>python build-all.py
Building machine 3axis_rs485.h
========================= [SUCCESS] Took 55.99 seconds =========================

Building machine 3axis_v3.h
========================= [SUCCESS] Took 23.42 seconds =========================

Building machine 3axis_v4.h
========================= [SUCCESS] Took 23.37 seconds =========================

Building machine 3axis_xyx.h
========================= [SUCCESS] Took 23.27 seconds =========================

Building machine 4axisexternaldriver.h
========================= [SUCCESS] Took 22.98 seconds =========================

Building machine 6packLowriderstepstickv1.h
========================= [SUCCESS] Took 23.19 seconds =========================

Building machine 6packMPCNCstepstickv1.h
========================= [SUCCESS] Took 23.71 seconds =========================

Building machine 6packstepstick_v1.h
========================= [SUCCESS] Took 22.92 seconds =========================

Building machine 6packstepstickXYZv1.h
========================= [SUCCESS] Took 23.05 seconds =========================

Building machine 6packtrinamic_stallguard.h
========================= [SUCCESS] Took 23.40 seconds =========================

Building machine atari_1020.h
========================= [SUCCESS] Took 23.24 seconds =========================

Building machine espduino.h
========================= [SUCCESS] Took 22.78 seconds =========================

Building machine i2soutxxyyzz.h
========================= [SUCCESS] Took 22.52 seconds =========================

Building machine i2soutxyzabc.h
========================= [SUCCESS] Took 23.15 seconds =========================

Building machine i2soutxyzabc_trinamic.h
========================= [SUCCESS] Took 23.67 seconds =========================

Building machine lowrider_v1p2.h
========================= [SUCCESS] Took 23.71 seconds =========================

Building machine midtbot.h
========================= [SUCCESS] Took 23.13 seconds =========================

Building machine mpcnclasermodule_v1p2.h
========================= [SUCCESS] Took 23.20 seconds =========================

Building machine mpcnc_v1p1.h
========================= [SUCCESS] Took 23.36 seconds =========================

Building machine mpcnc_v1p2.h
========================= [SUCCESS] Took 23.54 seconds =========================

Building machine pen_laser.h
========================= [SUCCESS] Took 23.80 seconds =========================

Building machine polar_coaster.h
========================= [SUCCESS] Took 23.54 seconds =========================

Building machine spidaisy4axis_xyyz.h
========================= [SUCCESS] Took 23.25 seconds =========================

Building machine spidaisy4axis_xyz.h
========================= [SUCCESS] Took 23.10 seconds =========================

Building machine spidaisy4axis_xyza.h
========================= [SUCCESS] Took 23.23 seconds =========================

Building machine tapster3.h
========================= [SUCCESS] Took 23.05 seconds =========================

Building machine template.h
========================= [SUCCESS] Took 23.01 seconds =========================

Building machine test_drive.h
========================= [SUCCESS] Took 22.95 seconds =========================

Building machine tmc2130_pen.h
========================= [SUCCESS] Took 22.88 seconds =========================