Fix use of LOAD= with WantSystemLib()...

third_party/libxslt/libxslt.scons

 # Copyright 2008, Google Inc.
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #    * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #    * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 Import('env')
 
 env = env.Clone()
 
+if env.WantSystemLib('libxslt'):
+    Return()
+
 env.Prepend(
     CPPPATH = [
         '$LIBXML_DIR/DerivedSources/include',
         '$LIBXML_DIR/include',
         '$ICU38_DIR/public/common',
         '$ICU38_DIR/public/18n',
         '$ZLIB_DIR',
         'scons',
         '.',
         '../',
@@ skipping 78 matching lines @@
       'config.h',
       'xslt-config',
       'libexslt/exsltconfig.h',
       'libxslt/xsltconfig.h',
       'libxslt/xsltwin32config.h',
   ]
   for cf in config_files:
     result = env.Command('scons/' + cf, 'linux/' + cf,
                          Copy('$TARGET', '$SOURCE'))