Fix premake copying directory tree on Unix

[victorpopkov]

Just a quick fix. cp default behaviour differs from xcopy when it comes to copying directory trees, as it only requires the destination directory without the directory name itself.

Outputs

Directory tree (before)

```txt build ├── dont_starve │ └── mods │ └── wand │ ├── exported │ │ └── wand │ └── images │ └── inventoryimages ├── linux │ └── mod_tools │ ├── buildtools │ │ └── linux │ │ └── Python27 │ │ └── Python27 │ │ └── Lib │ │ └── site-packages │ │ └── klei │ └── mod_tools │ ├── compiler_scripts │ ├── data │ ├── exported │ ├── scripts │ └── tools │ └── scripts └── proj ```

Directory tree (after)

```txt build ├── dont_starve │ └── mods │ └── wand │ ├── exported │ │ └── wand │ └── images │ └── inventoryimages ├── linux │ └── mod_tools │ ├── buildtools │ │ └── linux │ │ └── Python27 │ │ └── Lib │ │ └── site-packages │ │ └── klei │ ├── compiler_scripts │ ├── data │ ├── exported │ ├── scripts │ └── tools │ └── scripts └── proj ```

Premake output (before)

```txt Target OS not specified. Assuming it's the host OS. which "unzip" &>/dev/null mkdir -p "../build" /usr/bin/unzip mkdir -p "../build/dont_starve/mods" unzip -q -o "../pkg/tst/wand.zip" -d "../build/dont_starve/mods" mkdir -p "../build/linux/mod_tools" cp -r "../pkg/cmn/mod_tools" "../build/linux/mod_tools" mkdir -p "../build/linux/mod_tools/buildtools/linux/Python27" cp -r "../pkg/unix/Python27" "../build/linux/mod_tools/buildtools/linux/Python27" mkdir -p "../build/linux/mod_tools" cp -r "../pkg/unix/mod_tools" "../build/linux/mod_tools" Building configurations... Running action 'gmake'... Generating ../build/proj/Makefile... Generating ../build/proj/scml.make... Generating ../build/proj/png.make... Generating ../build/proj/autocompiler.make... Generating ../build/proj/modtoollib.make... Done. ```

Premake output (after)

```txt Target OS not specified. Assuming it's the host OS. which "unzip" &>/dev/null mkdir -p "../build" /usr/bin/unzip mkdir -p "../build/dont_starve/mods" unzip -q -o "../pkg/tst/wand.zip" -d "../build/dont_starve/mods" mkdir -p "../build/linux/mod_tools" cp -r "../pkg/cmn/mod_tools" "../build/linux/mod_tools/.." mkdir -p "../build/linux/mod_tools/buildtools/linux/Python27" cp -r "../pkg/unix/Python27" "../build/linux/mod_tools/buildtools/linux/Python27/.." mkdir -p "../build/linux/mod_tools" cp -r "../pkg/unix/mod_tools" "../build/linux/mod_tools/.." Building configurations... Running action 'gmake'... Generating ../build/proj/Makefile... Generating ../build/proj/scml.make... Generating ../build/proj/png.make... Generating ../build/proj/autocompiler.make... Generating ../build/proj/modtoollib.make... Done. ```

Tested on

• Linux (Ubuntu 20.04.3 LTS x86_64)
• macOS (macOS 11.5.2 20G95 x86_64)
• Windows (Windows 11 Pro 21H2 22000.176)