[netcdf-c] Fix dependency libmath

[JackBoosY]

Since netcdf-c requires the math library, the system in Linux also provides libm, but embree3 also generates the libmath library. Due to search order issues, embree's libmath library will be used first.

So change the math library name order to prevent the use of embree's math library.

Fixes #12169

[Neumann-A]

No that is incorrect. netcdf-c searches for any usable math library. This might be either libmath.a or a system provided libm.a. As such the CMakeLists.txt needs to differentiate between those two a bit more and have a option like USE_LIBMATH_INSTEAD_OF_LIBM/USE_EMBREE_LIBMATH or similar. It is not a necessity to build netcdf-c with libmath. A system provided libm would also be fine.

[JackBoosY]

@Neumann-A Yes, the math library can be provided by the system, but not necessarily.
We cannot determine whether the math library exists in the build environment, so we must rely on embree to ensure a smooth build.

[Neumann-A]

@JackBoosY: A lot of ports would fail in CI if -lm wouldn't be available.

If you change the order to
FIND_LIBRARY(HAVE_LIBM NAMES m libm math)
or simply remove math than you should have what is intended in netcdf-c. I think that it picked up libmath.a from embree was more by accident than by design

[Neumann-A]

considering that the commit introducing the find_library call does not even have a commit message and was 8 years ago.

[JackBoosY]

@Neumann-A Should be okay now.

[JackBoosY]

/azp run

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