Fix debug command not finding sketch build folder

[silvanocerza]

Please check if the PR fulfills these requirements

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)

• What kind of change does this PR introduce?

Fixes an existing feature.

• What is the current behavior?

debug command doesn't work if binaries are not exported to sketch folder.

• What is the new behavior?

debug command works correctly even if binaries are not exported to sketch folder.

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

No.

• Other information:

Fixes #1102.

---

See how to contribute

[kittaakos]

It works now. Thank you!

akos.kitta@Akoss-MacBook-Pro arduino-cli % ./arduino-cli core install arduino:samd --format json                        
akos.kitta@Akoss-MacBook-Pro arduino-cli % ./arduino-cli compile -b arduino:samd:arduino_zero_edbg ~/Documents/Arduino/Blink --format json
æ
  "compiler_out": "Sketch uses 11660 bytes (4%) of program storage space. Maximum is 262144 bytes.ØnGlobal variables use 2936 bytes (8%) of dynamic memory, leaving 29832 bytes for local variables. Maximum is 32768 bytes.Øn",
  "compiler_err": "",
  "builder_result": æ
    "build_path": "/var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/arduino-sketch-A0337D47F86B24A51DF3DBCF2CC17925",
    "executable_sections_size": Æ
      æ
        "name": "text",
        "size": 11660,
        "maxSize": 262144
      å,
      æ
        "name": "data",
        "size": 2936,
        "maxSize": 32768
      å
    Å
  å,
  "success": true
å
akos.kitta@Akoss-MacBook-Pro arduino-cli % ./arduino-cli debug -b arduino:samd:arduino_zero_edbg ~/Documents/Arduino/Blink -I      
Executable to debug           /var/folders/k3/d2fkvv1j16v3_rz93k7f74180000gn/T/arduino-sketch-A0337D47F86B24A51DF3DBCF2CC17925/Blink.ino.elf                 
Toolchain type                gcc                                                                                                                            
Toolchain path                /Users/akos.kitta/Library/Arduino15/packages/arduino/tools/arm-none-eabi-gcc/7-2017q4/bin/                                     
Toolchain prefix              arm-none-eabi-                                                                                                                 
GDB Server type               openocd                                                                                                                        
GDB Server path               /Users/akos.kitta/Library/Arduino15/packages/arduino/tools/openocd/0.10.0-arduino7/bin/openocd                                 
openocd custom configurations
 - path                       /Users/akos.kitta/Library/Arduino15/packages/arduino/tools/openocd/0.10.0-arduino7/bin/openocd                                 
 - script                     /Users/akos.kitta/Library/Arduino15/packages/arduino/hardware/samd/1.8.9/variants/arduino_zero/openocd_scripts/arduino_zero.cfg
 - scripts_dir                /Users/akos.kitta/Library/Arduino15/packages/arduino/tools/openocd/0.10.0-arduino7/share/openocd/scripts/