[flang] Add a set of tests which compile the predefined module files. Each...

[flang] Add a set of tests which compile the predefined module files. Each test simply tries to compile the module source file. Modify the script test_errors.sh to work with a source file that is specified as a full path. Also, change how the test temp directory is created to use a random name in case any of the source file base names are duplicated.

Original-commit: flang-compiler/f18@ec048ab1d528cf6ebc1d45767544201064b8fbe8
Reviewed-on: https://github.com/flang-compiler/f18/pull/522
Tree-same-pre-rewrite: false