CMakeLists: Fail for unmet dependencies

If (optional) feature/plugin is required, but the dependency is not
found, the build will fail.

Before the build process continued by (silently) disabling the
feature/plugin.

CMakeLists.txt

@@ -99,14 +99,11 @@ setByDefault(CPULOAD_PLUGIN Yes)
 if(CPULOAD_PLUGIN)
     find_library(STATGRAB_LIB statgrab)
 
-    if(NOT(${STATGRAB_LIB} MATCHES "NOTFOUND"))
-        list(APPEND ENABLED_PLUGINS "Cpu Load")
-        add_subdirectory(plugin-cpuload)
-  else()
-        message(STATUS "")
-        message(STATUS "CPU Load plugin requires libstatgrab")
-        message(STATUS "")
+    if(NOT STATGRAB_LIB)
+        message(FATAL_ERROR "CPU Load plugin requires libstatgrab")
     endif()
+    list(APPEND ENABLED_PLUGINS "Cpu Load")
+    add_subdirectory(plugin-cpuload)
 endif()
 
 setByDefault(DIRECTORYMENU_PLUGIN Yes)
@@ -161,14 +158,11 @@ setByDefault(SENSORS_PLUGIN Yes)
 if(SENSORS_PLUGIN)
     find_library(SENSORS_LIB sensors)
 
-    if(NOT(${SENSORS_LIB} MATCHES "NOTFOUND"))
-        list(APPEND ENABLED_PLUGINS "Sensors")
-        add_subdirectory(plugin-sensors)
-    else()
-        message(STATUS "")
-        message(STATUS "Sensors plugin requires lm_sensors")
-        message(STATUS "")
+    if(NOT SENSORS_LIB)
+        message(FATAL_ERROR "Sensors plugin requires lm_sensors")
     endif()
+    list(APPEND ENABLED_PLUGINS "Sensors")
+    add_subdirectory(plugin-sensors)
 endif()
 
 setByDefault(SHOWDESKTOP_PLUGIN Yes)
@@ -183,14 +177,11 @@ setByDefault(NETWORKMONITOR_PLUGIN Yes)
 if(NETWORKMONITOR_PLUGIN)
     find_library(STATGRAB_LIB statgrab)
 
-    if(NOT(${STATGRAB_LIB} MATCHES "NOTFOUND"))
-        list(APPEND ENABLED_PLUGINS "Network Monitor")
-        add_subdirectory(plugin-networkmonitor)
-    else()
-        message(STATUS "")
-        message(STATUS "Network Monitor plugin requires libstatgrab")
-        message(STATUS "")
+    if(NOT STATGRAB_LIB)
+        message(FATAL_ERROR "Network Monitor plugin requires libstatgrab")
     endif()
+    list(APPEND ENABLED_PLUGINS "Network Monitor")
+    add_subdirectory(plugin-networkmonitor)
 endif()
 
 setByDefault(SYSSTAT_PLUGIN Yes)
@@ -229,27 +220,25 @@ setByDefault(VOLUME_USE_ALSA Yes)
 if(VOLUME_PLUGIN)
     if (VOLUME_USE_PULSEAUDIO)
         find_package(PulseAudio)
+        if (NOT PULSEAUDIO_FOUND)
+            message(FATAL_ERROR "PulseAudio not found, but required (VOLUME_USE_PULSEAUDIO) for Volume plugin!")
+        endif ()
     endif(VOLUME_USE_PULSEAUDIO)
 
     if(VOLUME_USE_ALSA)
         find_package(ALSA)
+        if (NOT ALSA_FOUND)
+            message(FATAL_ERROR "ALSA not found, but required (VOLUME_USE_ALSA) for Volume plugin!")
+        endif ()
     endif()
 
-    if(PULSEAUDIO_FOUND OR ALSA_FOUND)
-        list(APPEND ENABLED_PLUGINS   "Volume")
-        message(STATUS "")
-        message(STATUS "Volume plugin will be built")
-        message(STATUS "    ALSA: ${ALSA_FOUND}")
-        message(STATUS "    PulseAudio: ${PULSEAUDIO_FOUND}")
-        message(STATUS "")
-        add_subdirectory(plugin-volume)
-    else()
-        message(STATUS "")
-        message(STATUS "Volume plugin requires pulseaudio or alsa")
-        message(STATUS "    ALSA: ${ALSA_FOUND}")
-        message(STATUS "    PulseAudio: ${PULSEAUDIO_FOUND}")
-        message(STATUS "")
-    endif()
+    list(APPEND ENABLED_PLUGINS   "Volume")
+    message(STATUS "")
+    message(STATUS "Volume plugin will be built")
+    message(STATUS "    ALSA: ${ALSA_FOUND}")
+    message(STATUS "    PulseAudio: ${PULSEAUDIO_FOUND}")
+    message(STATUS "")
+    add_subdirectory(plugin-volume)
 endif()
 
 setByDefault(WORLDCLOCK_PLUGIN Yes)