Make viewer compile on standalone linux x86_64

This involves making libllcommon shared, a change
that was not finished for windows/Mac.
More changes are needed to indra/newview/viewer_manifest.py
for those two operating systems, as well as to
indra/copy_win_scripts.

I did not test this on linux 32bit, nor non-standalone
on that OS, either.

I did not check voice (which will very likely not work
anyway on 64bit). And currently the webkit plugin doesn't
work for me, but I'll fix that in a different commit.

indra/cmake/LLCommon.cmake

@@ -7,9 +7,15 @@ include(ZLIB)
 
 set(LLCOMMON_INCLUDE_DIRS
     ${LIBS_OPEN_DIR}/llcommon
-    ${APRUTIL_INCLUDE_DIR}
     ${APR_INCLUDE_DIR}
     ${Boost_INCLUDE_DIRS}
     )
 
-set(LLCOMMON_LIBRARIES llcommon)
+if (LINUX)
+    # In order to support using ld.gold on linux, we need to explicitely
+    # specify all libraries that llcommon uses.
+    # llcommon uses `clock_gettime' which is provided by librt on linux.
+    set(LLCOMMON_LIBRARIES llcommon rt)
+else (LINUX)
+    set(LLCOMMON_LIBRARIES llcommon)
+endif (LINUX)