CMake: Allow overriding the CPack generator at configuration time

Author: tstenner

LSLCMake.cmake

@@ -294,23 +294,23 @@ macro(LSLGenerateCPackConfig)
 		set(CPACK_PACKAGE_NAME lsl)
 		set(CPACK_PACKAGE_VENDOR "Labstreaminglayer")
 		if(APPLE)
-			set(CPACK_GENERATOR "TBZ2")
+			set(LSL_CPACK_DEFAULT_GEN TBZ2)
 			if(DEFINED ENV{OSXVER})
 				# Configured by Travis-CI for multi-osx builds.
 				set(LSL_OS "$ENV{OSXVER}")
 			else()
 				set(LSL_OS "OSX${lslplatform}")
 			endif(DEFINED ENV{OSXVER})
 		elseif(WIN32)
-			set(CPACK_GENERATOR ZIP) # you can create NSIS packages by calling 'cpack -G NSIS'
+			set(LSL_CPACK_DEFAULT_GEN ZIP)
 			set(CPACK_NSIS_MODIFY_PATH ON)
 			set(CPACK_WIX_CMAKE_PACKAGE_REGISTRY ON)
 			set(CPACK_WIX_UPGRADE_GUID "ee28a351-3b27-4c2b-8b48-259c87d1b1b4")
 			set(CPACK_WIX_PROPERTY_ARPHELPLINK
 				"https://labstreaminglayer.readthedocs.io/info/getting_started.html#getting-help")
 			set(LSL_OS "Win${lslplatform}")
 		elseif(UNIX)
-			set(CPACK_GENERATOR DEB)
+			set(LSL_CPACK_DEFAULT_GEN DEB)
 			set(CPACK_SET_DESTDIR 1)
 			set(CPACK_INSTALL_PREFIX "/usr")
 			set(CPACK_DEBIAN_PACKAGE_MAINTAINER "Tristan Stenner <[email protected]>")
@@ -332,6 +332,7 @@ macro(LSLGenerateCPackConfig)
 			endif()
 			set(LSL_OS "Linux${lslplatform}-${LSB_RELEASE_CODENAME}")
 		endif()
+		set(CPACK_GENERATOR ${LSL_CPACK_DEFAULT_GEN} CACHE STRING "CPack pkg type(s) to generate")
 		get_cmake_property(CPACK_COMPONENTS_ALL COMPONENTS)
 		foreach(component ${CPACK_COMPONENTS_ALL})
 			string(TOUPPER ${component} COMPONENT)