On MacOS one can have different xcode versions installed. Switching between these versions for OpenJDK builds can be achieved either via switching the active xcode system-wide using xcode-select or by using the configure flag --with-toolchain-path.

In the latter case, however, the required value for the path is neither self-explaining nor well documented. It turns out that the toolchain path needs 2 components, <xcode_path>/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin and <xcode_path>/Contents/Developer/usr/bin to become effective.

To make it more convenient to pick a certain xcode for a certain build, I suggest adding a configure option --with-xcode-path that simply needs the path to the xcode installations, e.g. /Applications/Xcode.app.