Ninja: Prefer first ninja tool available in PATH

Brad Kingrequested to merge
brad.king/cmake:ninja-tool into master

We search for tools ninja-build, ninja, and samu as the build tool for the Ninja generator. Re-order the search to prefer whichever tool appears first in the PATH. This makes it easier for users to control which tool gets used when more than one is available.

Fixes: #20028 (closed)

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