CMake: Use GNUInstallDirs for install location defaults

CMakeLists.txt

@@ -13,6 +13,7 @@ INCLUDE (CheckSymbolExists)
 INCLUDE (CheckCSourceCompiles)
 INCLUDE (CheckStructHasMember)
 INCLUDE (CheckLibraryExists)
+INCLUDE (GNUInstallDirs)
 
 PROJECT (c-ares C)
 
@@ -42,19 +43,6 @@ SET (CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/lib)
 SET (CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_BINARY_DIR}/lib)
 SET (PACKAGE_DIRECTORY ${PROJECT_BINARY_DIR}/package)
 
-
-# Install path helpers
-IF (NOT DEFINED CARES_INSTALL_LOCATION_LIBS)
-	SET (CARES_INSTALL_LOCATION_LIBS ${CMAKE_INSTALL_PREFIX}/lib CACHE INTERNAL "")
-ENDIF ()
-IF (NOT DEFINED CARES_INSTALL_LOCATION_HEADERS)
-	SET (CARES_INSTALL_LOCATION_HEADERS ${CMAKE_INSTALL_PREFIX}/include CACHE INTERNAL "")
-ENDIF ()
-IF (NOT DEFINED CARES_INSTALL_LOCATION_BIN)
-	SET (CARES_INSTALL_LOCATION_BIN ${CMAKE_INSTALL_PREFIX}/bin CACHE INTERNAL "")
-ENDIF ()
-
-
 # Look for dependent/required libraries
 CHECK_LIBRARY_EXISTS (resolv res_servicename "" HAVE_RES_SERVICENAME_IN_LIBRESOLV)
 IF (HAVE_RES_SERVICENAME_IN_LIBRESOLV)
@@ -553,7 +541,7 @@ IF (CARES_SHARED)
 	TARGET_LINK_LIBRARIES (${PROJECT_NAME} PUBLIC ${CARES_DEPENDENT_LIBS})
 
 	IF (CARES_INSTALL)
-		INSTALL (TARGETS ${PROJECT_NAME} DESTINATION ${CARES_INSTALL_LOCATION_LIBS})
+		INSTALL (TARGETS ${PROJECT_NAME} DESTINATION ${CMAKE_INSTALL_LIBDIR})
 	ENDIF ()
 	SET (STATIC_SUFFIX "_static")
 
@@ -582,7 +570,7 @@ IF (CARES_STATIC)
 
 	TARGET_LINK_LIBRARIES (${LIBNAME} PUBLIC ${CARES_DEPENDENT_LIBS})
 	IF (CARES_INSTALL)
-		INSTALL (TARGETS ${LIBNAME} DESTINATION ${CARES_INSTALL_LOCATION_LIBS})
+		INSTALL (TARGETS ${LIBNAME} DESTINATION ${CMAKE_INSTALL_LIBDIR})
 	ENDIF ()
 
 	# For chain building: add alias targets that look like import libs that would be returned by find_package(Cares).
@@ -597,7 +585,7 @@ ENDIF ()
 # Headers installation target
 IF (CARES_INSTALL)
 	SET (CARES_HEADERS ares.h ares_version.h ares_dns.h "${PROJECT_BINARY_DIR}/ares_build.h" ares_rules.h)
-	INSTALL (FILES ${CARES_HEADERS} DESTINATION ${CARES_INSTALL_LOCATION_HEADERS})
+	INSTALL (FILES ${CARES_HEADERS} DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 ENDIF ()
 
 
@@ -612,7 +600,7 @@ ADD_EXECUTABLE (ahost ahost.c ${SAMPLESOURCES})
 TARGET_COMPILE_DEFINITIONS (ahost PRIVATE HAVE_CONFIG_H=1)
 TARGET_LINK_LIBRARIES (ahost PRIVATE ${PROJECT_NAME})
 IF (CARES_INSTALL)
-	INSTALL (TARGETS ahost RUNTIME DESTINATION ${CARES_INSTALL_LOCATION_BIN})
+	INSTALL (TARGETS ahost RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 ENDIF ()
 
 
@@ -621,7 +609,7 @@ ADD_EXECUTABLE (adig adig.c ${SAMPLESOURCES})
 TARGET_COMPILE_DEFINITIONS (adig PRIVATE HAVE_CONFIG_H=1)
 TARGET_LINK_LIBRARIES (adig PRIVATE ${PROJECT_NAME})
 IF (CARES_INSTALL)
-	INSTALL (TARGETS adig RUNTIME DESTINATION ${CARES_INSTALL_LOCATION_BIN})
+	INSTALL (TARGETS adig RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 ENDIF ()
 
 
@@ -630,5 +618,5 @@ ADD_EXECUTABLE (acountry acountry.c ${SAMPLESOURCES})
 TARGET_COMPILE_DEFINITIONS (acountry PRIVATE HAVE_CONFIG_H=1)
 TARGET_LINK_LIBRARIES (acountry PRIVATE ${PROJECT_NAME})
 IF (CARES_INSTALL)
-	INSTALL (TARGETS acountry RUNTIME DESTINATION ${CARES_INSTALL_LOCATION_BIN})
+	INSTALL (TARGETS acountry RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 ENDIF ()