Build process updated:

You have to specify `TARGET` to specify a configuration, e.g.

```
rake TARGET=host-debug all test
```

When you port `mruby` to a new configuration:
1. copy an existing configuration under `target` directory
2. modify the new configuration file
3. build using the new configuration
4. send PR if you please

1 files changed, 40 insertions, 0 deletions

diff --git a/target/travis.rb b/target/travis.rb
new file mode 100644
index 000000000..f4bef0a52
--- /dev/null
+++ b/target/travis.rb
@@ -0,0 +1,40 @@
+MRuby::Build.new('full-debug') do |conf|
+  toolchain :gcc
+  enable_debug
+
+  # include all core GEMs
+  conf.gembox 'full-core'
+  conf.cc.flags += %w(-Werror=declaration-after-statement)
+  conf.cc.defines += %w(MRB_GC_STRESS MRB_METHOD_CACHE MRB_ENABLE_DEBUG_HOOK)
+
+  conf.enable_test
+end
+
+MRuby::Build.new do |conf|
+  toolchain :gcc
+
+  # include all core GEMs
+  conf.gembox 'full-core'
+  conf.cc.flags += %w(-Werror=declaration-after-statement)
+  conf.compilers.each do |c|
+    c.defines += %w(MRB_GC_FIXED_ARENA)
+  end
+  conf.enable_bintest
+  conf.enable_test
+end
+
+MRuby::Build.new('cxx_abi') do |conf|
+  toolchain :gcc
+
+  conf.gembox 'full-core'
+  conf.cc.flags += %w(-fpermissive)
+  conf.compilers.each do |c|
+    c.defines += %w(MRB_GC_FIXED_ARENA)
+  end
+  conf.enable_bintest
+  conf.enable_test
+
+  enable_cxx_abi
+
+  build_mrbc_exec
+end