build(cmake): stop defaulting to Debug builds

[plexoos]

Remove the top-level CMAKE_BUILD_TYPE fallback that forced single-config generators such as Ninja and Makefiles into Debug when users did not pass an explicit build type.

This lets CMake preserve its standard empty build-type behavior and requires callers to choose Debug, Release, RelWithDebInfo, or MinSizeRel intentionally.

[Copilot]

Pull request overview

Removes the top-level CMAKE_BUILD_TYPE fallback that previously forced single-config generators (e.g., Ninja/Makefiles) into Debug when no build type was specified, restoring CMake’s standard “empty build type unless explicitly set” behavior.

Changes:

• Deleted the root-level logic that set CMAKE_BUILD_TYPE=Debug when unset for single-config generators.

Comments suppressed due to low confidence (1)

CMakeLists.txt:15

• This change makes single-config generators (Ninja/Makefiles) keep the default empty CMAKE_BUILD_TYPE unless the caller sets one. However, the repo's quick-start docs/examples still show configuring with cmake -S ... -B build without -DCMAKE_BUILD_TYPE=..., which now produces a different build than before (previously forced Debug). To match the PR description (“requires callers to choose … intentionally”) and avoid surprising builds, please update the build instructions (e.g., README + docs/getting-started + examples) to specify a recommended build type (Release/RelWithDebInfo) or explicitly document that leaving it unset is supported and what it implies.

project(simphony VERSION 0.7.0 LANGUAGES CXX CUDA)

# Use CMake's standard testing option, but avoid enabling this project's tests
# by default when Simphony is pulled in as a subproject.
if(NOT DEFINED BUILD_TESTING)
    set(BUILD_TESTING ${PROJECT_IS_TOP_LEVEL} CACHE BOOL "Build the testing tree.")
endif()

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