Expect tests to specify stderr content if it is present.
Fix the CMP0019 test, which has only been testing the WARN status
until now. Specify in the CommandLine and FPHSA tests that content
is at least one character.
Set policies in the Language and CheckModules tests, which have empty
test output, modulo unrelated policies on some platforms.
Set the minimum required version of CMake high enough to avoid the
warning for CMAKE_LEGACY_CYGWIN_WIN32. The warning appears on stderr
and breaks the expected output matching.
Since commit e1409ac5 (Support building shared libraries or modules
without soname, 2012-04-22) CMake crashes on the code
add_library(foo SHARED foo.nolang)
because the logic to lookup the language's soname flag was moved from
cmTarget::GetLibraryNames to cmMakefile::GetSONameFlag without its check
for a NULL language. Restore the check for NULL.
Add RunCMake.Languages test to cover language error cases like this one.