[cmake] Normalize TARGET_SUBDIR paths (#138524)

Some code paths normalize ".." and thus don't create the directory. But some execute in a
shell thus requiring the directory to exist to be able to take the parent directory.

This patch normalizes all the `TARGET_SUBDIR` variables to avoid this issue.

GitOrigin-RevId: fc3b67aee852d99bbb5d2f4670695d8246375dac