Spack: Correct fix_darwin_install_name (#2886)

Previously, fix_darwin_install_name would only handle dependencies that have no path set, and it ignore dependencies that have the build directory as path baked in. Catch this, and replace it by the install directory.

lib/spack/llnl/util/filesystem.py

@@ -455,7 +455,12 @@ def fix_darwin_install_name(path):
         # fix all dependencies:
         for dep in deps:
             for loc in libs:
-                if dep == os.path.basename(loc):
+                # We really want to check for either
+                #     dep == os.path.basename(loc)   or
+                #     dep == join_path(builddir, os.path.basename(loc)),
+                # but we don't know builddir (nor how symbolic links look
+                # in builddir). We thus only compare the basenames.
+                if os.path.basename(dep) == os.path.basename(loc):
                     subprocess.Popen(
                         ["install_name_tool", "-change", dep, loc, lib],
                         stdout=subprocess.PIPE).communicate()[0]