Enable installation only if top-level

I recently noticed that covfie tries to install itself even if it is not
the top level project, which is obviously problematic. This commit fixes
this behaviour, adding install rules only if the project is top level.

CMakeLists.txt

@@ -71,31 +71,33 @@ if(COVFIE_BUILD_EXAMPLES)
     add_subdirectory(examples)
 endif()
 
-# Installation logic.
-# CMake is hell.
-include(CMakePackageConfigHelpers)
-
-write_basic_package_version_file(
-    ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-    VERSION ${PROJECT_VERSION}
-    COMPATIBILITY SameMajorVersion
-)
-
-configure_package_config_file(
-    ${PROJECT_SOURCE_DIR}/cmake/${PROJECT_NAME}Config.cmake.in
-    ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
-    INSTALL_DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake
-)
-
-install(
-    EXPORT ${PROJECT_NAME}Targets
-    NAMESPACE ${PROJECT_NAME}::
-    DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake
-)
-
-install(
-    FILES
-        ${PROJECT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
-        ${PROJECT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-    DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake
-)
+if(PROJECT_IS_TOP_LEVEL)
+    # Installation logic.
+    # CMake is hell.
+    include(CMakePackageConfigHelpers)
+
+    write_basic_package_version_file(
+        ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+        VERSION ${PROJECT_VERSION}
+        COMPATIBILITY SameMajorVersion
+    )
+
+    configure_package_config_file(
+        ${PROJECT_SOURCE_DIR}/cmake/${PROJECT_NAME}Config.cmake.in
+        ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
+        INSTALL_DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake
+    )
+
+    install(
+        EXPORT ${PROJECT_NAME}Targets
+        NAMESPACE ${PROJECT_NAME}::
+        DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake
+    )
+
+    install(
+        FILES
+            ${PROJECT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
+            ${PROJECT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
+        DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/${PROJECT_NAME}/cmake
+    )
+endif()

lib/core/CMakeLists.txt

@@ -25,13 +25,15 @@ set_target_properties(
             core
 )
 
-install(TARGETS covfie_core EXPORT ${PROJECT_NAME}Targets)
+if(PROJECT_IS_TOP_LEVEL)
+    install(TARGETS covfie_core EXPORT ${PROJECT_NAME}Targets)
 
-install(
-    DIRECTORY
-        ${CMAKE_CURRENT_SOURCE_DIR}/covfie
-    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-)
+    install(
+        DIRECTORY
+            ${CMAKE_CURRENT_SOURCE_DIR}/covfie
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    )
+endif()
 
 # Hack for people using the disgusting mal-practice of pullling in external
 # projects via "add_subdirectory"...

lib/cpu/CMakeLists.txt

@@ -21,13 +21,15 @@ set_target_properties(
             cpu
 )
 
-install(TARGETS covfie_cpu EXPORT ${PROJECT_NAME}Targets)
+if(PROJECT_IS_TOP_LEVEL)
+    install(TARGETS covfie_cpu EXPORT ${PROJECT_NAME}Targets)
 
-install(
-    DIRECTORY
-        ${CMAKE_CURRENT_SOURCE_DIR}/covfie
-    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-)
+    install(
+        DIRECTORY
+            ${CMAKE_CURRENT_SOURCE_DIR}/covfie
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    )
+endif()
 
 target_link_libraries(covfie_cpu INTERFACE covfie_core)
 

lib/cuda/CMakeLists.txt

@@ -30,13 +30,15 @@ set_target_properties(
             cuda
 )
 
-install(TARGETS covfie_cuda EXPORT ${PROJECT_NAME}Targets)
+if(PROJECT_IS_TOP_LEVEL)
+    install(TARGETS covfie_cuda EXPORT ${PROJECT_NAME}Targets)
 
-install(
-    DIRECTORY
-        ${CMAKE_CURRENT_SOURCE_DIR}/covfie
-    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-)
+    install(
+        DIRECTORY
+            ${CMAKE_CURRENT_SOURCE_DIR}/covfie
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    )
+endif()
 
 # Hack for compatibility
 if(NOT PROJECT_IS_TOP_LEVEL)