I couldn't find a way to to make solaris-11-sparc platform definition take into
account the project, because of the way vanagon creates the Platform and then
later the Project. So create a new solaris-113-sparc platform definition for
native Solaris compiles.

Since the name of the file contains 113, vanagon assumes that's the
`os_version`. Setting the os_version from within the platform definition doesn't
seem to work, so I had to specialy case some logic to check for the
platform.name.

Although we're native compiling on SPARC, we have to explicitly set
`--with-baseruby=no` so that ruby's configure script does not attempt to use the
ancient ruby already installed. Instead build miniruby and have the build use
that. We should probably be setting `--with-baseruby=no` always, except in cases
where we're cross compiling to avoid this same problem on other platforms.

Similarly, ruby's configure script will attempt to enable `dtrace` because the
executable is present. Explicitly disable it.

The ruby-augeas gem's native extensions didn't work, because we were overriding
rbconfig when native compiling. It is only necessary to do that when cross
compiling, because the host ruby running on Solaris Intel needs to override CC,
etc configuration when installing gems with native extensions.

The ruby-shadow gem did work on SPARC, but it was relying on the rbconfig
overrides to find gcc. Instead add pl-build-tools to the PATH and only override
rbconfig when cross compiling.