Trilinos: Use more flexible option for locating the BLAS library directory. (#1987)

+ This change fixes a problem that manifests when trilinos is built against a
  MKL installation defined as an external package. In this scenario, the MKL
  libraries are found one directory deeper than for the case where spack
  provides MKL. The extra directory is a platform name like 'intel64'.
+ The changes in this PR were recommended by contributor @davydden. I
  implemented and tested with intel@16.0.3. These changes fix the issue I
  reported. I did not attempt building trilinos against other BLAS
  implementations.
+ fixes #1923

var/spack/repos/builtin/packages/mkl/package.py

@@ -66,13 +66,6 @@ def install(self, spec, prefix):
         for f in os.listdir(mkl_dir):
             os.symlink(os.path.join(mkl_dir, f), os.path.join(self.prefix, f))
 
-        # Unfortunately MKL libs are natively distrubted in prefix/lib/intel64.
-        # To make MKL play nice with Spack, symlink all files to prefix/lib:
-        mkl_lib_dir = os.path.join(prefix, "lib", "intel64")
-        for f in os.listdir(mkl_lib_dir):
-            os.symlink(os.path.join(mkl_lib_dir, f),
-                       os.path.join(self.prefix, "lib", f))
-
     def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         # set up MKLROOT for everyone using MKL package
         spack_env.set('MKLROOT', self.prefix)

var/spack/repos/builtin/packages/trilinos/package.py

@@ -149,10 +149,10 @@ def install(self, spec, prefix):
             '-DMPI_BASE_DIR:PATH=%s' % spec['mpi'].prefix,
             '-DTPL_ENABLE_BLAS=ON',
             '-DBLAS_LIBRARY_NAMES=%s' % ';'.join(blas.names),
-            '-DBLAS_LIBRARY_DIRS=%s' % spec['blas'].prefix.lib,
+            '-DBLAS_LIBRARY_DIRS=%s' % ';'.join(blas.directories),
             '-DTPL_ENABLE_LAPACK=ON',
             '-DLAPACK_LIBRARY_NAMES=%s' % ';'.join(lapack.names),
-            '-DLAPACK_LIBRARY_DIRS=%s' % spec['lapack'].prefix.lib,
+            '-DLAPACK_LIBRARY_DIRS=%s' % ';'.join(lapack.directories),
             '-DTrilinos_ENABLE_EXPLICIT_INSTANTIATION:BOOL=ON',
             '-DTrilinos_ENABLE_CXX11:BOOL=ON',
             '-DTPL_ENABLE_Netcdf:BOOL=ON',