Allow "hammer Hammer SHARED=1" to build cleanly.

build/SConscript.main

Index: build/SConscript.main
diff --git a/build/SConscript.main b/build/SConscript.main
index 44dcb208abaaef4a7c5d3caf58bba529229c2ab8..d6df2c382713a373bc8cf1cbf9ca9e27cf50bd07 100644
--- a/build/SConscript.main
+++ b/build/SConscript.main
@@ -540,6 +540,16 @@ if ARGUMENTS.get('SYMBOLS') == '1':
 if ARGUMENTS.get('SHARED') == '1':
   linux_env.Replace(COMPONENT_STATIC=False)
 
+  # The shared library build only works for test_shell and test_shell_tests,
+  # so filter out Chrome.
+  print "Filtering out chrome and media build targets in shared object build."
+  linux_env.FilterOut(
+      BUILD_SCONSCRIPTS = [
+          '$CHROME_DIR/chrome.scons',
+          '$MEDIA_DIR/media.scons',
+      ]
+  )
+
 # Build with system-provided NSS and GTK.
 if root_env['PLATFORM'] in ['linux', 'linux2', 'posix']:
   try: