Fix iOS and Mac builds due to issues with xcrun args and sys.command

Since pulling all the new sources since the OpenFL 1.1 release I have had issues building for iOS.  

* I traced this partially to a missing DEVELOPER_DIRECTORY.  So I fixed Tools.hx to also set DEVELOPER_DIR even if its not a legacy directory

Once doing this I saw issues such as xcrun command not found.  This seemed to stem from an issue with using "xcrun --sdk ..." as the exe value which eventually gets passed to haxe's sys.command.  

*  I edited the toolchain files for iOS and Mac to separate the --sdk and clang/g++ into flags.

There were still issues with the order of arguments passed to xcrun.  This is where I'm not sure if the changes are correct and input from @jgranick would be great.

* I changed the order of the compilation args in Compiler.hx  in the compile and precompile methods to have mFlags first.  Maybe this can be fixed by changing how the flags are defined in the toolchain.  Any input is welcome.