Fixes #1345 - do not buffer logging for native-image output

[nikolaylagutko]

Replace default BufferedLogger implementation of ProcessLogger with custom implementation that does not bufferize output - so the stdout of Process come to log immediately, but not at the Process exit

[lightbend-cla-validator]

Hi @nikolaylagutko,

Thank you for your contribution! We really value the time you've taken to put this together.

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[muuki88]

Changes look good. What issues where you having? Is the log completely empty during the build?

[nikolaylagutko]

@muuki88 the log is here, but it had printed output only when native-image command finished. As my build takes few minutes - it's much pretty to see the some log lines with process to be sure it working :-D
More detailed can be found here #1345