configure/cmake_linux.cmake: Fix CURL variable checking

It does not make sense to check

if(A)
...
elseif(A)
...
endif()

so let's change the elseif to an else.

Author: t-b

configure/cmake_linux.cmake

@@ -53,6 +53,6 @@ if(CURL)
             COMMAND ${CURL} -v -T ${CPACK_PACKAGE_FILE_NAME}.deb -u$ENV{BINTRAY_USER_NAME}:$ENV{BINTRAY_API_KEY} \"https://api.bintray.com/content/tango-controls/debian/cppTango/${LIBRARY_VERSION}/pool/main/libt/${LINUX_FLAVOUR}/${CPACK_PACKAGE_FILE_NAME}.deb\;deb_distribution=${LINUX_FLAVOUR}\;deb_component=main\;deb_architecture=${CPACK_DEBIAN_PACKAGE_ARCHITECTURE}\;publish=1\;override=1\"
             WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
             DEPENDS ${PROJECT_BINARY_DIR}/${CPACK_PACKAGE_FILE_NAME}.deb)
-elseif(CURL)
+else(CURL)
     message(WARNING "curl was not found deploy won't be possible")
 endif(CURL)