We need to do something about that error message.
It's a good idea.
First, it is not quite how works the "Autodetect" button - it simply reports that nothing is found and fills "Compiler install dir" with "C:\Program Files (x86)\GNUARM" value.
Next, The executable are under bin subdirectory of taken directory, but I can't understand, is path incorrect or something wrong then compiler tryed to run.
Third, what is strange restriction when binaries must be placed under "bin" subdirectory? I think, much better to point exact to directory which contains compiler executables.
Fourth, near all fields, near [...] button will be cool if one more button be placed, [AutoLocate] - pressing on it C::B looks for files in "compiler/install/dir/bin" with mack "*gcc", "*g++", "*ar", "*gdb" etc.