[BUG]: module being stripped if no build type selected (2.10.2 regression)

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What version (or hash if on master) of pybind11 are you using?

2.10.3

Problem description

If no CMAKE_BUILD_TYPE is specified, the seemingly innocuous quotes that were added in 88b019a8a5e116d7e4a4ffae6399a426364d4bcd cause the pybind11_add_module function to strip the module, even for debug builds.

By relying on CMAKE_BUILD_TYPE at configure time rather than on $<CONFIG> at generation time, multi-configuration generators like Ninja Multi-Config cannot work correctly. It might be better to use a generator expression (e.g. https://stackoverflow.com/questions/45455350/cmake-how-to-add-a-custom-command-that-is-only-executed-for-one-configuration).

Reproducible example code

CMakeLists.txt

cmake_minimum_required(VERSION 3.20)
project(test-project)

# Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
if(NOT MSVC AND NOT ${uppercase_CMAKE_BUILD_TYPE} MATCHES DEBUG|RELWITHDEBINFO)
    # Strip unnecessary sections of the binary on Linux/macOS
    message(STATUS "Without quotes: strip")
else()
    message(STATUS "Without quotes: no strip")
endif()

# Use case-insensitive comparison to match the result of $<CONFIG:cfgs>
string(TOUPPER "${CMAKE_BUILD_TYPE}" uppercase_CMAKE_BUILD_TYPE)
if(NOT MSVC AND NOT "${uppercase_CMAKE_BUILD_TYPE}" MATCHES DEBUG|RELWITHDEBINFO)
    # Strip unnecessary sections of the binary on Linux/macOS
    message(STATUS "With quotes:    strip")
else()
    message(STATUS "With quotes:    no strip")
endif()

Run CMake without build type

cmake -Bbuild -S.

-- Without quotes: no strip
-- With quotes:    strip

Is this a regression? Put the last known working version here if it is.

1f04cc7062e33481c62c78231e9561b318bca67b