"error: {build.pwmflags}: No such file or directory" with Curiosity Nano ATtiny1607 in Arduino IDE 2.3.4

[Locge]

I just got hold of a Curiosity Nano ATtiny1607 and installed the megaTinyCore in the Arduino IDE 2.3.4.
I started with the BareMinimum sketch and selected "Official Microchip Board".
As board name I obviously use "Curiosity Nano ATtiny1607" but then the compiler throws up an error:
avr-g++: error: {build.pwmflags}: No such file or directory
exit status 1

I had a go at the various options with "BOD Mode when Active/Sleeping", "Clock", "millis()/micros() Timer" but it doesn't make any difference.
Choosing the wrong Curiosity board, ATtiny3217 or ATtiny1627, clears the error.
I'm confused.

Can anyone help?

Edit:
I had the IDE show the command lines for "Compiling sketch..." when selecting two different Curiosity Nano boards:
"C:\Users\MyUserName\AppData\Local\Arduino15\packages\DxCore\tools\avr-gcc\7.3.0-atmel3.6.1-azduino7b1/bin/avr-g++" -c -g -Os -Wall -std=gnu++17 -fpermissive -Wno-sized-deallocation -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -MMD -flto -mrelax -mmcu=attiny1607 -DF_CPU=20000000L -DCLOCK_SOURCE=0 -DTWI_MORS -DMILLIS_USE_TIMERA0 -DCORE_ATTACH_ALL {build.pwmflags} -DARDUINO=10607 -DARDUINO_AVR_CuriosityNano1607 -DARDUINO_ARCH_MEGAAVR "-DMEGATINYCORE="2.6.10"" -DMEGATINYCORE_MAJOR=2UL -DMEGATINYCORE_MINOR=6UL -DMEGATINYCORE_PATCH=10UL -DMEGATINYCORE_RELEASED=1 -DARDUINO_attinyxy7 -DLED_BUILTIN=PIN_PC4 -DPIN_BUTTON_BUILTIN=PIN_PB7 "-IC:\Users\MyUserName\AppData\Local\Arduino15\packages\megaTinyCore\hardware\megaavr\2.6.10\cores\megatinycore/api/deprecated" "-IC:\Users\MyUserName\AppData\Local\Arduino15\packages\megaTinyCore\hardware\megaavr\2.6.10\cores\megatinycore" "-IC:\Users\MyUserName\AppData\Local\Arduino15\packages\megaTinyCore\hardware\megaavr\2.6.10\variants\txy7" "C:\Users\MyUserName\AppData\Local\arduino\sketches\DE94AC95B7C88887B8B6741E420BD13A\sketch\BareMinimum.ino.cpp" -o "C:\Users\MyUserName\AppData\Local\arduino\sketches\DE94AC95B7C88887B8B6741E420BD13A\sketch\BareMinimum.ino.cpp.o"

"C:\Users\MyUserName\AppData\Local\Arduino15\packages\DxCore\tools\avr-gcc\7.3.0-atmel3.6.1-azduino7b1/bin/avr-g++" -c -g -Os -Wall -std=gnu++17 -fpermissive -Wno-sized-deallocation -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -MMD -flto -mrelax -mmcu=attiny1627 -DF_CPU=20000000L -DCLOCK_SOURCE=0 -DTWI_MORS -DMILLIS_USE_TIMERB1 -DCORE_ATTACH_ALL -DARDUINO=10607 -DARDUINO_AVR_CuriosityNano1627 -DARDUINO_ARCH_MEGAAVR "-DMEGATINYCORE="2.6.10"" -DMEGATINYCORE_MAJOR=2UL -DMEGATINYCORE_MINOR=6UL -DMEGATINYCORE_PATCH=10UL -DMEGATINYCORE_RELEASED=1 -DARDUINO_attinyxy7 -DLED_BUILTIN=PIN_PB4 -DPIN_BUTTON_BUILTIN=PIN_PB7 "-IC:\Users\MyUserName\AppData\Local\Arduino15\packages\megaTinyCore\hardware\megaavr\2.6.10\cores\megatinycore/api/deprecated" "-IC:\Users\MyUserName\AppData\Local\Arduino15\packages\megaTinyCore\hardware\megaavr\2.6.10\cores\megatinycore" "-IC:\Users\MyUserName\AppData\Local\Arduino15\packages\megaTinyCore\hardware\megaavr\2.6.10\variants\txy7" "C:\Users\MyUserName\AppData\Local\arduino\sketches\DE94AC95B7C88887B8B6741E420BD13A\sketch\BareMinimum.ino.cpp" -o "C:\Users\MyUserName\AppData\Local\arduino\sketches\DE94AC95B7C88887B8B6741E420BD13A\sketch\BareMinimum.ino.cpp.o"
Is the parameter -DCORE_ATTACH_ALL {build.pwmflags} correct?

[per1234]

I already supported @Locge in this matter over on Arduino Forum, but for the benefit of anyone else who might be affected, I'll provide some information here as well:

The bug that caused the error was fixed by 3e3f820.

The fix was made after the time of the last release, so the fix will only be present when using a manual installation of the development version of the platform. Detailed instructions for installing the development version are available here:

https://forum.arduino.cc/t/compiler-error-build-pwmflags-no-such-file-or-directory-with-curiosity-nano-attiny1607/1353598/2