[Linux] Drop prebuilt freetype and fontconfig, use system libraries.

indra/cmake/ViewerMiscLibs.cmake

@@ -3,9 +3,6 @@ include(Prebuilt)
 
 if (NOT STANDALONE)
   use_prebuilt_binary(slvoice)
-  if(LINUX)
-    use_prebuilt_binary(fontconfig)
-  endif(LINUX)
 else (NOT STANDALONE)
   # Download there even when using standalone.
   set(STANDALONE OFF)
@@ -16,4 +13,9 @@ else (NOT STANDALONE)
   set(STANDALONE ON)
 endif(NOT STANDALONE)
 
+if(LINUX)
+  include(FindPkgConfig)
+  pkg_check_modules(FONTCONFIG REQUIRED fontconfig)
+endif(LINUX)
+
 use_prebuilt_binary(fonts)