Added a workaround to an issue when Windows is unable to return the date/time

Signed-off-by: Otavio Rodolfo Piske <opiske@redhat.com>

CMakeLists.txt

@@ -25,8 +25,20 @@ SET(PAHO_VERSION_MINOR 0)
 SET(PAHO_VERSION_PATCH 3)
 SET(CLIENT_VERSION ${PAHO_VERSION_MAJOR}.${PAHO_VERSION_MINOR}.${PAHO_VERSION_PATCH})
 
+# SET(BUILD_TIMESTAMP "")
 EXECUTE_PROCESS(COMMAND date -u OUTPUT_VARIABLE BUILD_TIMESTAMP)
+
+IF (BUILD_TIMESTAMP STREQUAL "")
+	MESSAGE(WARNING "Unable to determine build timestamp via default mechanism.")
+
+	IF (WIN32)
+		EXECUTE_PROCESS(COMMAND "cmd.exe" "/c" echo %DATE% %TIME% OUTPUT_VARIABLE BUILD_TIMESTAMP)
+	ENDIF()
+ENDIF()
+
 STRING(STRIP ${BUILD_TIMESTAMP} BUILD_TIMESTAMP)
+MESSAGE(STATUS "Timestamp is ${BUILD_TIMESTAMP}")
+
 
 # Uses the correct directory for libraries on Red Hat-based distributions.
 SET(PAHO_LIBRARY_DIR_NAME "lib")