Incorrect compiler error when using --source-override

[kittaakos]

Bug Report

This is a follow-up of #1099.

Current behavior

--source-override generates an incorrect compiler error.

Actual:

 % ls -al
total 16
drwxr-xr-x   4 akos.kitta  staff   128 Feb 12 13:33 .
drwxr-xr-x@ 51 akos.kitta  staff  1632 Feb 12 13:32 ..
-rw-r--r--   1 akos.kitta  staff    96 Feb 12 13:37 overrides.json
-rw-r--r--   1 akos.kitta  staff    30 Feb 12 13:36 sketch_override.ino
 % cat sketch_override.ino 
void setup() {}
void loop() {}%                                                                                                                                                             
 % cat overrides.json 
{
    "overrides": {
        "sketch_override.ino": "foovoid setup() {}\nvoid loop() {}"
    }
}%                                                                                                                                                                          
 % arduino-cli compile -b arduino:avr:uno --source-override overrides.json
/Users/akos.kitta/Desktop/sketch_override/sketch_override.ino:1:1: error: 'foovoid' does not name a type; did you mean 'void'?
 void setup() {}
 ^~~~~~~
 void
/Users/akos.kitta/Desktop/sketch_override/sketch_override.ino:1:1: error: 'foovoid' does not name a type; did you mean 'void'?
 void setup() {}
 ^~~~~~~
 void

Error during build: exit status 1
 % 

Expected:

 % ls -al
total 16
drwxr-xr-x   4 akos.kitta  staff   128 Feb 12 13:33 .
drwxr-xr-x@ 51 akos.kitta  staff  1632 Feb 12 13:32 ..
-rw-r--r--   1 akos.kitta  staff    96 Feb 12 13:37 overrides.json
-rw-r--r--   1 akos.kitta  staff    30 Feb 12 13:36 sketch_override.ino
 % cat sketch_override.ino 
void setup() {}
void loop() {}%                                                                                                                                                             
 % cat overrides.json 
{
    "overrides": {
        "sketch_override.ino": "foovoid setup() {}\nvoid loop() {}"
    }
}%                                                                                                                                                                          
 % arduino-cli compile -b arduino:avr:uno --source-override overrides.json
/Users/akos.kitta/Desktop/sketch_override/sketch_override.ino:1:1: error: 'foovoid' does not name a type; did you mean 'void'?
 foovoid setup() {}
 ^~~~~~~
 void
/Users/akos.kitta/Desktop/sketch_override/sketch_override.ino:1:1: error: 'foovoid' does not name a type; did you mean 'void'?
 foovoid setup() {}
 ^~~~~~~
 void
Error during build: exit status 1
 % 

Environment

• CLI version (output of arduino-cli version): 0.34.2
• OS and platform: all

Additional context