Fix preprocess output (do not print stats after the preprocessed source)

[cmaglie]

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What kind of change does this PR introduce?

Do not print compilation stats at the end of the compile --preprocess output.

What is the current behavior?

$ arduino-cli compile -b arduino:avr:uno ~/Arduino/Blink/ --preprocess
#include <Arduino.h>
#line 1 "/home/megabug/Arduino/Blink/Blink.ino"
#line 1 "/home/megabug/Arduino/Blink/Blink.ino"
void setup();
#line 3 "/home/megabug/Arduino/Blink/Blink.ino"
void loop();
#line 1 "/home/megabug/Arduino/Blink/Blink.ino"
void setup() {
}
void loop() {
}


Used platform Version Path                                                        
arduino:avr   1.8.6   /home/megabug/.arduino15/packages/arduino/hardware/avr/1.8.6
$

What is the new behavior?

$ arduino-cli compile -b arduino:avr:uno ~/Arduino/Blink/ --preprocess
#include <Arduino.h>
#line 1 "/home/megabug/Arduino/Blink/Blink.ino"
#line 1 "/home/megabug/Arduino/Blink/Blink.ino"
void setup();
#line 3 "/home/megabug/Arduino/Blink/Blink.ino"
void loop();
#line 1 "/home/megabug/Arduino/Blink/Blink.ino"
void setup() {
}
void loop() {
}

$

Does this PR introduce a breaking change, and is titled accordingly?

No

Other information

Fix #2150

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.02 🎉

Comparison is base (7b774e1) 62.42% compared to head (d0b5ea6) 62.45%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2152      +/-   ##
==========================================
+ Coverage   62.42%   62.45%   +0.02%     
==========================================
  Files         224      224              
  Lines       19516    19520       +4     
==========================================
+ Hits        12183    12191       +8     
+ Misses       6235     6231       -4     
  Partials     1098     1098              

Flag	Coverage Δ
unit	62.45% <100.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
internal/cli/compile/compile.go	67.27% <100.00%> (+0.40%)	⬆️

... and 1 file with indirect coverage changes

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