fix: hide installation behind an option (#512)

Currently, every project pulling in SQLiteCpp automatically gets an
`make install` which installs SQLiteCpp into the system. This is often
not desired, since other projects only statically link. The solution is
to add another "SQLITECPP_INSTALL" option, which allows to turn on/off
this behavior.

Author: SRombauts

CMakeLists.txt

@@ -363,30 +363,32 @@ target_include_directories(SQLiteCpp
     $<INSTALL_INTERFACE:include/>)
 
 # Allow the library to be installed via "make install" and found with "find_package"
-
-include(GNUInstallDirs)
-install(TARGETS SQLiteCpp
-    EXPORT ${PROJECT_NAME}Targets
-    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    COMPONENT libraries)
-install(DIRECTORY include/ DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} COMPONENT headers FILES_MATCHING REGEX ".*\\.(hpp|h)$")
-install(EXPORT ${PROJECT_NAME}Targets DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
-install(FILES ${PROJECT_SOURCE_DIR}/package.xml DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROJECT_NAME})
-
-include(CMakePackageConfigHelpers)
-write_basic_package_version_file(
-    cmake/${PROJECT_NAME}ConfigVersion.cmake
-    VERSION ${PROJECT_VERSION}
-    COMPATIBILITY AnyNewerVersion)
-configure_package_config_file(
-    cmake/${PROJECT_NAME}Config.cmake.in
-    cmake/${PROJECT_NAME}Config.cmake
-    INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
-install(FILES
-    ${CMAKE_CURRENT_BINARY_DIR}/cmake/${PROJECT_NAME}Config.cmake
-    ${CMAKE_CURRENT_BINARY_DIR}/cmake/${PROJECT_NAME}ConfigVersion.cmake
-    DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
+option(SQLITECPP_INSTALL "Enables the install target." ON)
+if (SQLITECPP_INSTALL)
+    include(GNUInstallDirs)
+    install(TARGETS SQLiteCpp
+        EXPORT ${PROJECT_NAME}Targets
+        LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+        ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+        COMPONENT libraries)
+    install(DIRECTORY include/ DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} COMPONENT headers FILES_MATCHING REGEX ".*\\.(hpp|h)$")
+    install(EXPORT ${PROJECT_NAME}Targets DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
+    install(FILES ${PROJECT_SOURCE_DIR}/package.xml DESTINATION ${CMAKE_INSTALL_DATADIR}/${PROJECT_NAME})
+
+    include(CMakePackageConfigHelpers)
+    write_basic_package_version_file(
+        cmake/${PROJECT_NAME}ConfigVersion.cmake
+        VERSION ${PROJECT_VERSION}
+        COMPATIBILITY AnyNewerVersion)
+    configure_package_config_file(
+        cmake/${PROJECT_NAME}Config.cmake.in
+        cmake/${PROJECT_NAME}Config.cmake
+        INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
+    install(FILES
+        ${CMAKE_CURRENT_BINARY_DIR}/cmake/${PROJECT_NAME}Config.cmake
+        ${CMAKE_CURRENT_BINARY_DIR}/cmake/${PROJECT_NAME}ConfigVersion.cmake
+        DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
+endif (SQLITECPP_INSTALL)
 
 # Optional additional targets: