CI (Alpine): Use reference BLAS and LAPACK.

Some SuiteSparse libraries rely heavily on OpenMP. But the version of
OpenBLAS that is distributed by Alpine Linux is built without OpenMP.
This could lead to deadlocks (and OpenBLAS is very verbose about that
risk):
> OpenBLAS Warning : Detect OpenMP Loop and this application may hang. Please rebuild the library with USE_OPENMP=1 option.

Use the reference implementations of the BLAS and LAPACK libraries
instead (which might be slower than OpenBLAS but safer on that
distribution).

.github/workflows/build-arch-emu.yaml

@@ -67,7 +67,7 @@ jobs:
             m4
             gmp-dev
             mpfr-dev
-            openblas-dev
+            lapack-dev
             valgrind
 
       - name: prepare ccache
@@ -117,7 +117,7 @@ jobs:
                   -DCMAKE_C_COMPILER_LAUNCHER="ccache" \
                   -DCMAKE_CXX_COMPILER_LAUNCHER="ccache" \
                   -DCMAKE_Fortran_COMPILER_LAUNCHER="ccache" \
-                  -DBLA_VENDOR="OpenBLAS" \
+                  -DBLA_VENDOR="Generic" \
                   -DCOMPACT=ON \
                   ..
             echo "::endgroup::"
@@ -167,7 +167,7 @@ jobs:
           printf "::group::\033[0;32m==>\033[0m Configuring example\n"
           cmake \
             -DCMAKE_PREFIX_PATH="${GITHUB_WORKSPACE}/lib/cmake" \
-            -DBLA_VENDOR="OpenBLAS" \
+            -DBLA_VENDOR="Generic" \
             ..
           echo "::endgroup::"
           printf "::group::\033[0;32m==>\033[0m Building example\n"