Switching to "Always Copy Build Output to Intermediate"
solves the problem.
So, it seems concern with long command line.

It would be useful to see another verbose output with it working. The previous one shows it failed on the linker.

The copy to intemediate is a read only local copy of the final build output that happens after a successful build. Therefore unconnected to the linker issue.

This is the command that failed previously

n/arm-none-eabi-g++" "-LD:\ArduinoSeeed\Proj\Wio\I2C_Scanner\Release\" -Os -Wl,--gc-sections -save-temps terminal/linker_scripts/gcc/flash_with_bootloader.ld" "-Wl,-Map,D:\ArduinoSeeed\Proj\Wio\I2C_Scanner\Release\/I2C_Scanner.ino.map" --specs=nano.specs --specs=nosys.specs -mcpu=cortex-m4 -mthumb -Wl,--cref -Wl,--check-sections -Wl,--gc-sections -Wl,--unresolved-symbols=report-all -Wl,--warn-common -Wl,--warn-section-align -u _printf_float -u _scanf_float -Wl,--wrap,_write -u __wrap__write -o "D:\ArduinoSeeed\Proj\Wio\I2C_Scanner\Release\/I2C_Scanner.ino.elf" "D:\ArduinoSeeed\Proj\Wio\I2C_Scanner\Release\I2C_Scanner.cpp.o" "D:\ArduinoSeeed\Proj\Wio\I2C_Scanner\Release\Wire\Wire.cpp.o" 365211\variant\variant.cpp.o" -Wl,--start-group terminal" -larm_cortexM4lf_math -mfloat-abi=hard -mfpu=fpv4-sp-d16 terminal" -lm "D:\ArduinoSeeed\Proj\Wio\I2C_Scanner\Release\/core.a" -Wl,--end-group 

Thanks, this is the linker command that worked. We will compare them to see how the differ. At a quick glance they look the same which might suggest a virus checker or other background external task was temporarily prevent access to some of the files. Did you just see the error one time or multiple times before the issue resolved?

n/arm-none-eabi-g++" rminal\Release" -Os -Wl,--gc-sections -save-temps terminal/linker_scripts/gcc/flash_with_bootloader.ld" _wio_terminal\Release/I2C_Scanner.ino.map" --specs=nano.specs --specs=nosys.specs -mcpu=cortex-m4 -mthumb -Wl,--cref -Wl,--check-sections -Wl,--gc-sections -Wl,--unresolved-symbols=report-all -Wl,--warn-common -Wl,--warn-section-align -u _printf_float -u _scanf_float -Wl,--wrap,_write -u __wrap__write -o inal\Release/I2C_Scanner.ino.elf" "I2C_Scanner.cpp.o" "Wire\Wire.cpp.o" 365211\variant\variant.cpp.o" -Wl,--start-group terminal" -larm_cortexM4lf_math -mfloat-abi=hard -mfpu=fpv4-sp-d16 terminal" -lm inal\Release/core.a" -Wl,--end-group 

Sounds like the config was the same each time. What virus checker and anti-malware do you use? Some can lock files for a few seconds after they are created which then prevents the files from being found by the linkers.

I looked at your output and see in the first failed attempts the temp build folder had been overriden to conflict with the project folder and especially with the default intermediate folder. 

//initial attempts failed when the temp build folder was set to the same location as the project.
//

Compiling 'I2C_Scanner' for 'Seeeduino Wio Terminal'
Build Folder: "file:///D:/ArduinoSeeed/Proj/Wio/I2C_Scanner/Release/" 

//later attempts worked
//

Compiling 'I2C_Scanner' for 'Seeeduino Wio Terminal'
Build Folder: wio_terminal/Release" 

It seems everything is configured for Arduino portable mode but the build folder was set incorrectly. When overriding the  temp build folder it should be set to a different location to the intermediate folder otherwise unpredicable results might occurr. The temp build folder should also not be located within the project folder structure.

In you last working attempt it looks like the temp build folder has been set back to default (empty)?