GHA: use all cores for parallel compilation of Openblas on Windows

Author: dweindl

scripts/compileBLAS.cmd

@@ -9,6 +9,6 @@ cmake -S . -B build ^
     -DCMAKE_C_COMPILER:FILEPATH=cl ^
     -DCMAKE_BUILD_TYPE=Release ^
     -DCMAKE_MAKE_PROGRAM=ninja
-cmake --build build --parallel 2
+cmake --build build --parallel
 cmake --install build
 echo compileBLAS.cmd completed