Add YAML_CPP_INSTALL option for disabling install target (#624) (#625)

- Option defaults to ON and setting it to OFF, disables install
  target generation

CMakeLists.txt

@@ -24,6 +24,7 @@ set(YAML_CPP_VERSION "${YAML_CPP_VERSION_MAJOR}.${YAML_CPP_VERSION_MINOR}.${YAML
 option(YAML_CPP_BUILD_TESTS "Enable testing" ON)
 option(YAML_CPP_BUILD_TOOLS "Enable parse tools" ON)
 option(YAML_CPP_BUILD_CONTRIB "Enable contrib stuff in library" ON)
+option(YAML_CPP_INSTALL "Enable generation of install target" ON)
 
 ## Build options
 # --> General
@@ -299,12 +300,14 @@ if(MSVC)
 	endif()
 endif()
 
-install(TARGETS yaml-cpp EXPORT yaml-cpp-targets ${_INSTALL_DESTINATIONS})
-install(
-	DIRECTORY ${header_directory}
-	DESTINATION ${INCLUDE_INSTALL_DIR}
-	FILES_MATCHING PATTERN "*.h"
-)
+if (YAML_CPP_INSTALL)
+	install(TARGETS yaml-cpp EXPORT yaml-cpp-targets ${_INSTALL_DESTINATIONS})
+	install(
+		DIRECTORY ${header_directory}
+		DESTINATION ${INCLUDE_INSTALL_DIR}
+		FILES_MATCHING PATTERN "*.h"
+	)
+endif()
 
 export(
     TARGETS yaml-cpp
@@ -322,6 +325,7 @@ else()
 	set(INSTALL_CMAKE_DIR ${LIB_INSTALL_DIR}/cmake/yaml-cpp)
 endif()
 
+
 file(RELATIVE_PATH REL_INCLUDE_DIR "${CMAKE_INSTALL_PREFIX}/${INSTALL_CMAKE_DIR}" "${CMAKE_INSTALL_PREFIX}/${INCLUDE_INSTALL_ROOT_DIR}")
 set(CONFIG_INCLUDE_DIRS "\${YAML_CPP_CMAKE_DIR}/${REL_INCLUDE_DIR}")
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/yaml-cpp-config.cmake.in
@@ -330,16 +334,19 @@ configure_file(${CMAKE_CURRENT_SOURCE_DIR}/yaml-cpp-config.cmake.in
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/yaml-cpp-config-version.cmake.in
 	"${PROJECT_BINARY_DIR}/yaml-cpp-config-version.cmake" @ONLY)
 
-install(FILES
-	"${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/yaml-cpp-config.cmake"
-	"${PROJECT_BINARY_DIR}/yaml-cpp-config-version.cmake"
-	DESTINATION "${INSTALL_CMAKE_DIR}" COMPONENT dev)
-install(EXPORT yaml-cpp-targets DESTINATION ${INSTALL_CMAKE_DIR})
+if (YAML_CPP_INSTALL)
+	install(FILES
+		"${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/yaml-cpp-config.cmake"
+		"${PROJECT_BINARY_DIR}/yaml-cpp-config-version.cmake"
+		DESTINATION "${INSTALL_CMAKE_DIR}" COMPONENT dev)
+	install(EXPORT yaml-cpp-targets DESTINATION ${INSTALL_CMAKE_DIR})
+
+	if(UNIX)
+		set(PC_FILE ${CMAKE_BINARY_DIR}/yaml-cpp.pc)
+		configure_file("yaml-cpp.pc.cmake" ${PC_FILE} @ONLY)
+		install(FILES ${PC_FILE} DESTINATION ${LIB_INSTALL_DIR}/pkgconfig)
+	endif()
 
-if(UNIX)
-	set(PC_FILE ${CMAKE_BINARY_DIR}/yaml-cpp.pc)
-	configure_file("yaml-cpp.pc.cmake" ${PC_FILE} @ONLY)
-	install(FILES ${PC_FILE} DESTINATION ${LIB_INSTALL_DIR}/pkgconfig)
 endif()