[flang] Compile the output of -fdebug-unparse-with-modules (#135696)

The output of a compilation with the -fdebug-unparse-with-modules option
comprises its normal unparsed output along with the regenerated contents
of any modules that were required from module files. This is handy for
producing stand-alone test cases.

The modules' contents are generated by the same code that writes module
files, so they can contain some USE associations to private entities in
other modules that are necessary to complete local declarations, usually
initializers. Such USE associations to private entities are not flagged
as fatal errors when modules are read from module files, but they
currently are caught when the output produced by this option is being
read back in to the compiler.

Handle this case by softening the error to a warning when one module
uses a private entity from another with an alias containing the
non-conforming '$' character. (I could have omitted the message
altogether, but there are other valid warnings that will occur due to
undefined function result variables; further, I didn't want to provide a
general hole around the protection of private names.)

0 files changed, 0 insertions, 0 deletions