RunCMake: Allow specifying the source dir and file to test.

This will allow decoupling the name of the test from the name and
location of the source file under test, which means one source
file can be used for multiple tests.

Rename the PARENT_SCOPE test in RunCMake.set to not use a keyword
of the if() command as a file name.  As the filename is now used
with an if condition, this causes a conflict.
Export: Disallow exported interface includes in src/build tree (#14592).

Allow directories in the build tree only if they are also
subdirectories of the install tree.

Re-use the test files in the RunCMake.include_directories test
to run in multiple scenarios.  Bump the required CMake version
in the test to 3.0 to ensure that the new policy warnings are
emitted correctly.
Merge topic 'install-prefix-in-interface' into next

4d87d6e4 Export: Disallow exported interface includes in src/build tree (#14592).
c869984e RunCMake: Allow specifying the source dir and file to test.