cmake PROJECT_IS_TOP_LEVEL (#252)

This reverts commit f6b9b7f.

This commit needs to include package manager creation for conan and
vcpkg before it can be merged since it broke building for at lesat
conan.

CMakeLists.txt

@@ -22,9 +22,7 @@ if (NOT "$ENV{version}" STREQUAL "")
 endif()
 
 option(LIBCORO_EXTERNAL_DEPENDENCIES "Use Cmake find_package to resolve dependencies instead of embedded libraries, Default=OFF." OFF)
-option(LIBCORO_BUILD_TESTS           "Build the tests, Default=ON." ON)
 option(LIBCORO_CODE_COVERAGE         "Enable code coverage, tests must also be enabled, Default=OFF" OFF)
-option(LIBCORO_BUILD_EXAMPLES        "Build the examples, Default=ON." ON)
 option(LIBCORO_RUN_GITCONFIG         "Set the githooks directory to auto format and update the readme, Default=OFF." OFF)
 option(LIBCORO_BUILD_SHARED_LIBS     "Build shared libraries, Default=OFF." OFF)
 
@@ -37,8 +35,19 @@ if (LIBCORO_RUN_GITCONFIG)
     )
 endif()
 
-cmake_dependent_option(LIBCORO_FEATURE_NETWORKING "Include networking features, Default=ON." ON "NOT EMSCRIPTEN; NOT MSVC" OFF)
-cmake_dependent_option(LIBCORO_FEATURE_TLS "Include TLS encryption features, Default=ON." ON "NOT EMSCRIPTEN; NOT MSVC" OFF)
+if (CMAKE_VERSION VERSION_GREATER_EQUAL 3.21)
+    set(LIBCORO_PROJECT_IS_TOP_LEVEL "${PROJECT_IS_TOP_LEVEL}")
+else()
+    get_property(not_top DIRECTORY PROPERTY PARENT_DIRECTORY)
+    if(NOT not_top)
+        set(LIBCORO_PROJECT_IS_TOP_LEVEL true)
+    endif()
+endif()
+
+cmake_dependent_option(LIBCORO_BUILD_TESTS "Build the tests, Default=ON." ON "LIBCORO_PROJECT_IS_TOP_LEVEL" OFF)
+cmake_dependent_option(LIBCORO_BUILD_EXAMPLES "Build the examples, Default=ON." ON "LIBCORO_PROJECT_IS_TOP_LEVEL" OFF)
+cmake_dependent_option(LIBCORO_FEATURE_NETWORKING "Include networking features, Default=ON." ON "NOT EMSCRIPTEN; LINUX" OFF)
+cmake_dependent_option(LIBCORO_FEATURE_TLS "Include TLS encryption features, Default=ON." ON "NOT EMSCRIPTEN; LINUX" OFF)
 
 message("${PROJECT_NAME} LIBCORO_EXTERNAL_DEPENDENCIES = ${LIBCORO_EXTERNAL_DEPENDENCIES}")
 message("${PROJECT_NAME} LIBCORO_BUILD_TESTS           = ${LIBCORO_BUILD_TESTS}")