[llvm][compiler-rt] Connect lit dependencies to test-depends targets. (#81783)

compiler-rt was creating the test-depends targets and trying to fill its
dependencies with a variable, but the variable was empty because it was
supposed to take its value from a property. The changes in this commit
grab the value of the property and add them as dependencies.

The changes in llvm are to remove the usage of `DEPENDS` arguments from
`add_custom_target`, which according to the documentation is reserved
for files/outputs created by `add_custom_command`. Use
`add_dependencies` instead.

This is similar to the changes introduced in
4eb84582 for runtimes.