Fix clang/travis, prefer static libs when BOOST_ROOT is set.

.travis.yml

@@ -12,6 +12,11 @@ before_install:
   - sudo apt-get install -qq libboost1.55-all-dev 
   # We want debug symbols for boost as we install gdb later
   - sudo apt-get install -qq libboost1.55-dbg
+  - | # Setup the BOOST_ROOT
+      export BOOST_ROOT=$HOME/boost_root
+      mkdir -p $BOOST_ROOT/stage
+      ln -s /usr/lib/x86_64-linux-gnu $BOOST_ROOT/stage/lib
+      ln -s /usr/include/boost $BOOST_ROOT/boost
   - sudo apt-get install -qq mlocate
   - sudo updatedb
   - sudo locate libboost | grep /lib | grep -e ".a$"

SConstruct

@@ -199,6 +199,7 @@ def config_base(env):
         env.Append(LIBPATH=[
             os.path.join(BOOST_ROOT, 'stage', 'lib'),
             ])
+        env['BOOST_ROOT'] = BOOST_ROOT
     except KeyError:
         pass
 
@@ -262,15 +263,24 @@ def config_env(toolchain, variant, env):
                 '-Wno-unused-but-set-variable'
                 ])
 
-        env.Append(LIBS=[
+        boost_libs = [
             'boost_date_time',
             'boost_filesystem',
             'boost_program_options',
             'boost_regex',
             'boost_system',
-            'boost_thread',
-            'dl',
-            ])
+            'boost_thread'
+        ]
+        # We prefer static libraries for boost
+        if env.get('BOOST_ROOT'):
+            static_libs = ['%s/stage/lib/lib%s.a' % (env['BOOST_ROOT'], l) for
+                           l in boost_libs]
+            if all(os.path.exists(f) for f in static_libs):
+                boost_libs = [File(f) for f in static_libs]
+
+        env.Append(LIBS=boost_libs)
+        env.Append(LIBS=['dl'])
+
         if Beast.system.osx:
             env.Append(LIBS=[
                 'crypto',