cmake build: don't hardcode absolute paths in install DESTINATIONs

Fixes #683

> Currently, the CMakeLists.txt and *.conf_install.cmake.in files contain
> absolute install paths, that is, not relative to ${CMAKE_INSTALL_PREFIX}.
> This makes packaging this program unusually hard.

Signed-off-by: Alain Zscheile <zseri.devel@ytrizja.de>

CMakeLists.txt

@@ -324,9 +324,9 @@ configure_file (
 install(SCRIPT logrotate.conf_install.cmake)
 
 install(FILES org.kernel.TCMUService1.service
-  DESTINATION /usr/share/dbus-1/system-services)
-install(FILES tcmu-runner.conf DESTINATION /etc/dbus-1/system.d)
+  DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/dbus-1/system-services)
+install(FILES tcmu-runner.conf DESTINATION ${CMAKE_INSTALL_SYSCONFDIR}/dbus-1/system.d)
 if (SUPPORT_SYSTEMD)
-  install(FILES tcmu-runner.service DESTINATION /usr/lib/systemd/system/)
+  install(FILES tcmu-runner.service DESTINATION ${CMAKE_INSTALL_PREFIX}/lib/systemd/system)
 endif (SUPPORT_SYSTEMD)
-install(FILES tcmu-runner.8 DESTINATION ${CMAKE_INSTALL_PREFIX}/share/man/man8)
+install(FILES tcmu-runner.8 DESTINATION ${CMAKE_INSTALL_MANDIR}/man8)

logrotate.conf_install.cmake.in

@@ -1,4 +1,4 @@
-if (EXISTS "/etc/logrotate.d/tcmu-runner")
-	file(INSTALL "/etc/logrotate.d/tcmu-runner" DESTINATION "/etc/logrotate.d/tcmu-runner.bak" RENAME "tcmu-runner")
+if (EXISTS "${CMAKE_INSTALL_SYSCONFDIR}/logrotate.d/tcmu-runner")
+	file(INSTALL "${CMAKE_INSTALL_SYSCONFDIR}/logrotate.d/tcmu-runner" DESTINATION "${CMAKE_INSTALL_SYSCONFDIR}/logrotate.d/tcmu-runner.bak" RENAME "tcmu-runner")
 endif()
-file(INSTALL "${PROJECT_SOURCE_DIR}/logrotate.conf" DESTINATION "/etc/logrotate.d" RENAME "tcmu-runner")
+file(INSTALL "${PROJECT_SOURCE_DIR}/logrotate.conf" DESTINATION "${CMAKE_INSTALL_SYSCONFDIR}/logrotate.d" RENAME "tcmu-runner")

tcmu.conf_install.cmake.in

@@ -1,4 +1,4 @@
-if (EXISTS "/etc/tcmu/tcmu.conf")
-	file(INSTALL "/etc/tcmu/tcmu.conf" DESTINATION "/etc/tcmu/" RENAME "tcmu.conf.old")
+if (EXISTS "${CMAKE_INSTALL_SYSCONFDIR}/tcmu/tcmu.conf")
+	file(INSTALL "${CMAKE_INSTALL_SYSCONFDIR}/tcmu/tcmu.conf" DESTINATION "${CMAKE_INSTALL_SYSCONFDIR}/tcmu/" RENAME "tcmu.conf.old")
 endif()
-file(INSTALL "${PROJECT_SOURCE_DIR}/tcmu.conf" DESTINATION "/etc/tcmu/")
+file(INSTALL "${PROJECT_SOURCE_DIR}/tcmu.conf" DESTINATION "${CMAKE_INSTALL_SYSCONFDIR}/tcmu")