Compilation error 1.8.5

Hi,
I'm using the IDE on Windows 10.
Although I'm getting this error with 1.8.5 it also occurred previously with 1.6.x

Arduino : 1.8.5 (Windows 10), Carte : "Arduino/Genuino 101"

C:\Users\Pete\AppData\Local\Arduino15\packages\Intel\tools\arc-elf32\1.6.9+1.0.1/bin/arc-elf32-ar: unable to rename 'C:\Users\Pete\AppData\Local\Temp\arduino_build_909727\core\core.a'; reason: File exists

Utilisation de la bibliothèque Adafruit_GFX_Library version 1.2.2 dans le dossier: C:\Users\Pete\Documents\Arduino\libraries\Adafruit_GFX_Library
Utilisation de la bibliothèque arduino_903324 version 1.1.2 dans le dossier: C:\Users\Pete\Documents\Arduino\libraries\arduino_903324
Utilisation de la bibliothèque Adafruit_NeoPixel version 1.1.3 dans le dossier: C:\Users\Pete\Documents\Arduino\libraries\Adafruit_NeoPixel
exit status 1
Erreur de compilation pour la carte Arduino/Genuino 101

I also think that the IDE is seriously sub-optimal since it recompiles everything even if you've just changed the sketch you're working on. Why?

This inabilty to create the file goes away if I reboot.

Best regards,
Pete

This may be caused by your antivirus software. Try disabling it TEMPORARILY for a single compilation to see if it goes away. If so you will need to whitelist the offending process.

Regarding recompiling: The Arduino IDE should cache the compiled libraries including the core and only recompile if one of the files have been changed or you have changed the board setting. The sketch is preprocessed and compiled every time. If you're encountering other behavior then that's a bug.

I have just switched computers from Win7 to Win10 and pulled everything over ( Copied) from my old computer. When I first tried to compile a Blank test .ino with UNO, I got this error. I read thru the forums and thought it might be a Anti Virus program problem.. BUT on another forum it suggested running the Arduino.exe as Admin. I did and it worked on the blank. I then tried it on a Blink two LED's on an ESP32 and it also worked. Seems like I'll have to start running the program as Admin!