arpack: add option to use macOS Accelerate

Copy darwin flags `-ff2c -fno-second-underscore` from workflow to use
Accelerate without segfaulting / failing tests and enable the Accelerate
framework when `useAccel` is true.
https://github.com/opencollab/arpack-ng/blob/804fa3149a0f773064198a8e883bd021832157ca/.github/workflows/jobs.yml#L184-L192

pkgs/by-name/ar/arpack/package.nix

@@ -4,11 +4,13 @@
 , mpi
 , openssh
 , igraph
+, useAccel ? false #use Accelerate framework on darwin
 }:
 
 # MPI version can only be built with LP64 interface.
 # See https://github.com/opencollab/arpack-ng#readme
 assert useMpi -> !blas.isILP64;
+assert useAccel -> stdenv.hostPlatform.isDarwin;
 
 stdenv.mkDerivation rec {
   pname = "arpack";
@@ -22,11 +24,11 @@ stdenv.mkDerivation rec {
   };
 
   nativeBuildInputs = [ cmake gfortran ninja ];
-  buildInputs = assert (blas.isILP64 == lapack.isILP64); [
-    blas
-    lapack
+  buildInputs = [
     eigen
-  ] ++ lib.optional useMpi mpi;
+  ] ++ lib.optionals (!useAccel) (assert (blas.isILP64 == lapack.isILP64); [
+    blas lapack
+  ]) ++ lib.optional useMpi mpi;
 
   nativeCheckInputs = lib.optional useMpi openssh;
 
@@ -34,21 +36,26 @@ stdenv.mkDerivation rec {
   doCheck = true;
   enableParallelChecking = false;
 
+  env = lib.optionalAttrs useAccel {
+    # Without these flags some tests will fail / segfault when using Accelerate
+    # framework. They were pulled from the CI Workflow
+    # https://github.com/opencollab/arpack-ng/blob/804fa3149a0f773064198a8e883bd021832157ca/.github/workflows/jobs.yml#L184-L192
+    FFLAGS = "-ff2c -fno-second-underscore";
+  };
+
   cmakeFlags = [
     (lib.cmakeBool "BUILD_SHARED_LIBS" stdenv.hostPlatform.hasSharedLibraries)
     (lib.cmakeBool "EIGEN" true)
     (lib.cmakeBool "EXAMPLES" true)
     (lib.cmakeBool "ICB" true)
-    (lib.cmakeBool "INTERFACE64" blas.isILP64)
+    (lib.cmakeBool "INTERFACE64" (!useAccel && blas.isILP64))
     (lib.cmakeBool "MPI" useMpi)
   ] ++ lib.optionals stdenv.hostPlatform.isDarwin [
-    # prevent cmake from using Accelerate, which causes single precision tests
-    # to segfault
-    "-DBLA_VENDOR=Generic"
+    "-DBLA_VENDOR=${if useAccel then "Apple" else "Generic"}"
   ];
 
   passthru = {
-    inherit (blas) isILP64;
+    isILP64 = !useAccel && blas.isILP64;
     tests = {
       inherit igraph;
     };