Set libdir in generated .la files

This is needed in order to get libtool to treat them as normal
libraries and not "convenience libraries". The latter are linked
with --whole-archive, which pulls a lot of unnecessary stuff into
Xvnc and libvnc.so.
diff --git a/cmake/Modules/CMakeMacroLibtoolFile.cmake b/cmake/Modules/CMakeMacroLibtoolFile.cmake
index f2ea7f8..a54d994 100644
--- a/cmake/Modules/CMakeMacroLibtoolFile.cmake
+++ b/cmake/Modules/CMakeMacroLibtoolFile.cmake
@@ -130,7 +130,7 @@
   file(APPEND ${_laname} "shouldnotlink=no\n\n")
   file(APPEND ${_laname} "dlopen=''\n")
   file(APPEND ${_laname} "dlpreopen=''\n\n")
-  file(APPEND ${_laname} "libdir=''\n\n")
+  file(APPEND ${_laname} "libdir='/usr/lib'\n\n")
 
 
   # Add custom command to symlink the static library so that autotools finds