execute all build tests in the top-level rake context instead of spawning subprocesses

build_tests/clone_env/build.rb

@@ -1,11 +0,0 @@
-debug = Rscons::Environment.new do |env|
-  env.build_dir('src', 'debug')
-  env['CFLAGS'] = '-O2'
-  env['CPPFLAGS'] = '-DSTRING="Debug Version"'
-  env.Program('program-debug', Dir['src/*.c'])
-end
-
-release = debug.clone('CPPFLAGS' => '-DSTRING="Release Version"') do |env|
-  env.build_dir('src', 'release')
-  env.Program('program-release', Dir['src/*.c'])
-end