Update module output directory command for flang-new/f18

[awvwgk]

Currently the new LLVM flang driver is mistaken for the classic flang driver and therefore it fails with

❯ fpm build --compiler flang-new -C example_packages/hello_fpm
fpm: Entering directory '/home/awvwgk/projects/src/git/fortran-package-manager/example_packages/hello_fpm'
 + mkdir -p build/dependencies
 + mkdir -p build/flang-new_00000000811C9DC5/hello_fpm
 + flang-new -c ./../hello_complex/source/subdir/constants.f90  -module build/flang-new_00000000811C9DC5/hello_fpm -I build/flang-new_00000000811C9DC5/hello_fpm  -o build/flang-new_00000000811C9DC5/hello_fpm/.._hello_complex_source_subdir_constants.f90.o

With this patch we can run the flang-new driver and get the expected error due to missing code generation:

❯ ./fpm-flang build --compiler flang-new -C example_packages/hello_fpm
fpm: Entering directory '/home/awvwgk/projects/src/git/fortran-package-manager/example_packages/hello_fpm'
 + mkdir -p build/dependencies
 + mkdir -p build/flang-new_00000000811C9DC5
 + mkdir -p build/flang-new_00000000811C9DC5/hello_fpm/
 + flang-new -c ./../hello_complex/source/subdir/constants.f90  -module-dir build/flang-new_00000000811C9DC5 -Ibuild/flang-new_00000000811C9DC5 -o build/flang-new_00000000811C9DC5/hello_fpm/.._hello_complex_source_subdir_constants.f90.o
error: code-generation is not available yet

The f18 driver is less picky and takes -J, -module and -module-dir to specify the module output directory, I went with the latter since this is apparently in line with flang-new.

---

Note that there is flang in LLVM flang which is not the classic flang compiler, but presumably an internal component for the flang-new / f18 drivers (or maybe the other way round?). We will currently detect it as classic flang and fail with

❯ ./fpm-flang build --compiler flang -C example_packages/hello_fpm
fpm: Entering directory '/home/awvwgk/projects/src/git/fortran-package-manager/example_packages/hello_fpm'
 + mkdir -p build/flang_00000000811C9DC5
 + mkdir -p build/flang_00000000811C9DC5/hello_fpm/
 + flang -c ../hello_complex/source/subdir/constants.f90  -module build/flang_00000000811C9DC5 -Ibuild/flang_00000000811C9DC5 -o build/flang_00000000811C9DC5/hello_fpm/.._hello_complex_source_subdir_constants.f90.o
error: unknown argument: '-module build/flang_00000000811C9DC5'
flang: in /home/awvwgk/projects/src/git/fortran-package-manager/example_packages/hello_fpm, flang-new failed with exit status 1: /usr/bin/flang-new -fc1 -Ibuild/flang_00000000811C9DC5 -module-suffix .f18.mod -fdebug-unparse -fno-analyzed-objects-for-unparse -module-dir build/flang_00000000811C9DC5 -c ../hello_complex/source/subdir/constants.f90 -module build/flang_00000000811C9DC5 -Ibuild/flang_00000000811C9DC5 -o build/flang_00000000811C9DC5/hello_fpm/.._hello_complex_source_subdir_constants.f90.o

But I can't figure out how I'm supposed to correctly use it anyway.

[LKedward]

LGTM, cheers 👍