Basic.hx

class Basic {
    static function main() {
        trace('basic example');
    }
}

basic.hxml

-main Basic
-cpp cpp

build project

sven$ haxe -version
3.2.0
Svens-Mac-mini:haxe-basic sven$ haxelib path hxcpp
/Users/sven/dev/hxcpp/
-D hxcpp
Svens-Mac-mini:haxe-basic sven$ cd ~/dev/hxcpp/ && git pull && cd ~/dev/haxe-basic/
Already up-to-date.
Svens-Mac-mini:haxe-basic sven$ haxe basic.hxml 
haxelib run hxcpp Build.xml haxe -Dhaxe3="1" -Dhaxe_ver="3.2" -Dhxcpp_api_level="313" -I"/usr/lib/haxe/extraLibs/" -I"/usr/local/lib/haxe/extraLibs/" -I"" -I"/usr/lib/haxe/std/cpp/_std/" -I"/usr/local/lib/haxe/std/cpp/_std/" -I"/usr/lib/haxe/std/" -I"/usr/local/lib/haxe/std/"
sh: neko run.n Build.xml haxe -Dhaxe3=1 -Dhaxe_ver=3.2 -Dhxcpp_api_level=313 -I/usr/lib/haxe/extraLibs/ -I/usr/local/lib/haxe/extraLibs/ -I -I/usr/lib/haxe/std/cpp/_std/ -I/usr/local/lib/haxe/std/cpp/_std/ -I/usr/lib/haxe/std/ -I/usr/local/lib/haxe/std/ /Users/sven/dev/haxe-basic/cpp/: No such file or directory
Error: Build failed
Svens-Mac-mini:haxe-basic sven$ ls /Users/sven/dev/haxe-basic/cpp/
Build.xml	Options.txt	include		src

hxcpp clean

sven$ pwd
/Users/sven/dev/hxcpp/project
Svens-Mac-mini:project sven$ neko build.n clean
haxelib run hxcpp Build.xml clean -DHXCPP_CLEAN_ONLY
sh: neko run.n Build.xml clean -DHXCPP_CLEAN_ONLY /Users/sven/dev/hxcpp/project/: No such file or directory
#### Error cleaning

info.md

above errors are from version haxe_2015-01-28_development_8d1cc78.tar.gz

rolled back to haxe_2015-01-27_development_456a1a8.tar.gz worked,

now resulting call is haxe basic.hxml haxelib run hxcpp Build.xml haxe -Dhaxe3="1" -Dhaxe_ver="3.2" -Dhxcpp_api_level="313" -I"/usr/lib/haxe/extraLibs/" -I"/usr/local/lib/haxe/extraLibs/" -I"" -I"/usr/lib/haxe/std/cpp/_std/" -I"/usr/local/lib/haxe/std/cpp/_std/" -I"/usr/lib/haxe/std/" -I"/usr/local/lib/haxe/std/"

Note the blank -I"" as well!