clang-tidy with precompiled headers and cmake does not work - c++

Question

I have a simple setup where CMake produces the following compile command:
cd /workspaces/cmake-general/tests/project/build/examples/hello-world && /usr/local/bin/cmake -E __run_co_compile
--iwyu=/usr/local/bin/include-what-you-use
--tidy="/usr/bin/clang-tidy;-extra-arg=-Wno-unknown-warning-option;-warnings-as-errors=*;--extra-arg-before=--driver-mode=g++"
--source=/workspaces/cmake-general/tests/project/build/examples/hello-world/CMakeFiles/example-hello-world.dir/cmake_pch.hxx.cxx --
/usr/bin/c++
-I/workspaces/cmake-general/tests/project/examples/hello-world/src
-I/workspaces/cmake-general/tests/project/build -O3 -DNDEBUG -stdlib=libc++
-fcolor-diagnostics -Wall -Wextra -Wshadow -Wnon-virtual-dtor -Wold-style-cast -Wcast-align -Wunused -Woverloaded-virtual -Wpedantic -Wconversion
-Wsign-conversion -Wnull-dereference -Wdouble-promotion
-Wformat=2 -Werror -std=c++20 -Winvalid-pch -fpch-instantiate-templates
-Xclang -emit-pch -Xclang -include
-Xclang /workspaces/cmake-general/tests/project/build/examples/hello-world/CMakeFiles/example-hello-world.dir/cmake_pch.hxx
-x c++-header -MD -MT examples/hello-world/CMakeFiles/example-hello-world.dir/cmake_pch.hxx.pch -MF
CMakeFiles/example-hello-world.dir/cmake_pch.hxx.pch.d -o CMakeFiles/example-hello-world.dir/cmake_pch.hxx.pch
-c /workspaces/cmake-general/tests/project/build/examples/hello-world/CMakeFiles/example-hello-world.dir/cmake_pch.hxx.cxx
which errors our with not finding
/workspaces/cmake-general/tests/project/build/examples/example-sanitizer/CMakeFiles/example-sanitizer-address.dir/cmake_pch.hxx:5:10: error: 'iostream' file not found [clang-diagnostic-error]
#include <iostream>
^
3 errors generated.
When I take --tidy="..." stuff out of the command. It fully compiles, (also if I dont specify PCHs in the CMakeLists.txt) it works.
I am not sure what the problem is exactly.
Do PCH and clang-tidy somehow not work? Why are the include directories somehow missing? I am using LLVM-12, clang-12 on Ubuntu.
Also adding -I/usr/lib/llvm-12/include/c++/v1 does not help.