build: GSL and ns3/CMake fixes

Includes:
- add GSL include directories and libraries for wifi
- expose enable/disable GSL option in ns3
- refactor ns3 options list
- cmake formatting

src/nix-vector-routing/examples/CMakeLists.txt

@@ -20,12 +20,12 @@ foreach(
 endforeach()
 
 build_lib_example(
-    NAME nix-double-wifi
-    SOURCE_FILES nix-double-wifi.cc
-    LIBRARIES_TO_LINK
-      ${libpoint-to-point}
-      ${libwifi}
-      ${libapplications}
-      ${libinternet}
-      ${libnix-vector-routing}
-  )
+  NAME nix-double-wifi
+  SOURCE_FILES nix-double-wifi.cc
+  LIBRARIES_TO_LINK
+    ${libpoint-to-point}
+    ${libwifi}
+    ${libapplications}
+    ${libinternet}
+    ${libnix-vector-routing}
+)

src/wifi/CMakeLists.txt

@@ -1,3 +1,11 @@
+set(gsl_libraries)
+if(${GSL_FOUND})
+  include_directories(${GSL_INCLUDE_DIRS})
+  set(gsl_libraries
+      ${GSL_LIBRARIES}
+  )
+endif()
+
 set(source_files
     helper/athstats-helper.cc
     helper/spectrum-wifi-helper.cc
@@ -283,6 +291,7 @@ build_lib(
     ${libspectrum}
     ${libantenna}
     ${libmobility}
+    ${gsl_libraries}
   TEST_SOURCES
     test/block-ack-test-suite.cc
     test/channel-access-manager-test.cc