Documentation Fix

[andrej]

I noticed a very minor issue in the docs. I would have opened a PR instead of an issue with the fix, but I can't seem to find the source for the docs.

On this page: https://xilinx.github.io/XRT/master/html/build.html
Under section "Building the XRT Runtime", it says:

build.sh script builds for both Debug and Release profiles.

I think this is no longer accurate. At least on my end, I have to pass the -opt flag to get a Release build. Suggested change:

The build.sh script builds for the Debug profile by default. To get a Release build, pass the -opt flag.

The help for build.sh --help would also need to be updated, from:

[-dbg] Build debug library only (default)
[-opt] Build optimized library only (default)

to

[-dbg] Build debug library only (default)
[-opt] Build optimized library only

Like I said, very minor, but thought I'd let you know.