I found a temporary workaround. If in the cmd window I put the "path" command
c:\esp32\mkm\hello_world>path C:/Program Files/Java/jre1.8.0_241/bin/server;C:/Program Files/Java/jre1.8.0_241/bin;[cut...];C:\esp32\esp-idf\tools;C:\esp32\esp-idf;C:\esp32\eclipse
the "idf.py menuconfig" and "idf.py ...

It still doesn't work. I get an error:
Python requirements from C:\esp32\esp-idf\requirements.txt are satisfied.
Warn about uninitialized values.
-- Found Git: C:/Program Files/Git/cmd/git.exe (found version "2.25.1.windows.1")
-- IDF_TARGET not set, using default target: esp32
-- Building for ...

Hi Kubuś, this seems to be a different error than the one reported by drwill. Can you please try running "xtensa-esp32-elf-ld -v" from IDF command prompt and see if that works?

It works, I think:
c:\esp32\esp-idf\xtensa-esp32-elf-ld -v
GNU ld (crosstool-NG esp-2019r2) 2.31.1

But "idf.py ...

I've got the same error.
Warn about uninitialized values.
-- Found Git: C:/Program Files/Git/cmd/git.exe (found version "2.25.1.windows.1")
-- IDF_TARGET not set, using default target: esp32
-- The C compiler identification is GNU 8.2.0
-- The CXX compiler identification is GNU 8.2.0
-- The ASM ...