Linker and CC flags are incompatible on OSX

[abouteiller]

Describe the bug

Some flags that are valid for CC are not valid for the linker on OSX (this may also impact other platforms, although not seen in the wild).

To Reproduce

Steps to reproduce the behavior:

1. Checkout version a5f49ab2a (HEAD -> master, origin/master) Merge pull request #644 from abouteiller/bugfix/no-gpu-found..Bouteiller
2. ../dplasma/configure --prefix=/Users/bouteill/Devel/parsec/dplasma.openblas-gnu.debug --enable-debug=paranoid\,noisier --with-blas=OpenBLAS --with-platform=macosx --enable-prof-trace --with-python=python3 M4=gm4
3. code compiles, but loads of warnings spat out [2892/3249] Building C object tests/CMakeFiles/testing_zlange.dir/testing_zlange.c.o cc1: note: '-g3' is not supported by the debug linker in use (set to 2)

Expected behavior

No warnings

Solution

The CC_FLAGS and LINK_FLAGS need to be separated, just like we separated the FC_FLAGS and CXX_FLAGS.