Force compilation with gfortran to use O0 on older Loongson hardware to avoid spurious test failures

There are two instances when building the tests where OpenBLAS fails to
build with OpenMP and clang due to library paths getting reset as flags
are set rather than appended. This seems to only affect certain
clang/libomp installations, but if it's already grabbing the correct
library paths we might as well use them.

* Add C conversions of the CBLAS tests for NOFORTRAN=1 builds

* Enable CTEST without Fortran and fix passing of BUILD_vartype options to exports/gensymbol

The main Makefile takes care of this in the build process, but users or CI jobs may try to run this directly

Signed-off-by: Timothy Gu <timothygu99@gmail.com>

When OpenBLAS is compiled with USE_OPENMP=1, it ignores OPENBLAS_NUM_THREADS and GOTO_NUM_THREADS flags.Therefore, you should use OMP_NUM_THREADS.

Without setting OMP_NUM_THREADS, a process will use maximal number of threads on a computing node. Thus, if there are 2 processes on the computing node, the thread will contend against other threads on CPU cores. As a result, the application will hang.