amdflang compilation has several unexpected errors when makefile is run with multiple threads

[andrewkallai]

Describe the bug
When make is run with a -j value greater than one, and FC(fortran compiler)=amdflang, there is evident failure of tests which are otherwise expected to pass.

To Reproduce
make FC=amdflang -j >1

The expected fix will involve modifying the flags supplied to amdflang in the makefile.

[andrewkallai]

After looking into the flags amdflang provides, there does not seem to be a simple way (i.e., using a flag) to fix this issue. Currently, the amdflang provided in rocm/6.4.1 is an implementation based off of flang-classic. AMD however has begun development on a fortran compiler that is based off of LLVM flang. The pre-release of the compiler source is available at: https://repo.radeon.com/rocm/misc/flang/
The assumption is that this compiler would function equivalently to how LLVM flang does, meaning no additional flags would need to be provided than the ones for "flang-new" (will need to be renamed to flang in the makefile). As the case for the flang-classic implementation, it is advised to use single threading, as the current runs of the test suite do.