Travis: Use pip to install SCons on OSX

Not sure why we switched from homebrew to scons-local anymore,
but pip should work just fine and is recommended by upstream.

Downloads of scons-local from SourceForge were quite iffy, so
this should help avoid CI errors due to not having downloaded
SCons successfully.

Setting Python's user binary PATH seems necessary on Travis/OSX
as per travis-ci/travis-ci#5030 (confirmed that 'scons' is not
in PATH without it).

.travis.yml

@@ -87,7 +87,8 @@ install:
       misc/travis/android-tools-linux.sh;
     fi
   - if [ "$TRAVIS_OS_NAME" = "osx" ]; then
-      misc/travis/scons-local-osx.sh;
+      pip install --user scons;
+      export PATH=${PATH}:/Users/travis/Library/Python/2.7/bin;
     fi
   - if [ "$TRAVIS_OS_NAME" = "osx" ] && [ "$PLATFORM" = "android" ]; then
       misc/travis/android-tools-osx.sh;

misc/travis/scons-local-osx.sh

@@ -1,18 +0,0 @@
-#!/bin/bash
-
-echo
-echo "Download and install Scons local package ..."
-echo
-
-echo "Downloading sources ..."
-curl -L -O https://downloads.sourceforge.net/scons/scons-local-3.0.1.zip # latest version available here: http://scons.org/pages/download.html
-
-echo "Extracting to build directory ..."
-unzip -qq -n scons-local-3.0.1.zip -d $TRAVIS_BUILD_DIR/scons-local
-
-echo "Installing symlinks ..."
-ln -s $TRAVIS_BUILD_DIR/scons-local/scons.py /usr/local/bin/scons
-
-echo
-echo "Done!"
-echo