cmake: allow disabling building with the install name directory

When custom install names and rpaths setups are used they may not
work in the build tree as-is (namely when using absolute paths for
install names in order to avoid rpath juggling in downstream projects).

Add a flag for opting out of this behaviour.

GitOrigin-RevId: c1ce21b450fd9607c3b44acd520f4e449c6a9a89
2 files changed