libpciaccess: Convert to AutotoolsPackage, remove Darwin work-around (#3459)

* libpciaccess: Convert to AutotoolsPackage, remove Darwin work-around

Other packages that depend on libpciaccess can do so via a conditional dependency (via a variant); we don’t need a dummy package for Darwin any more.

* Disable libpciaccess dependency on non-Darwin platforms

* hwloc: Remove direct dependency on libpciaccess

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

@@ -25,7 +25,7 @@
 from spack import *
 
 
-class Libpciaccess(Package):
+class Libpciaccess(AutotoolsPackage):
     """Generic PCI access library."""
 
     homepage = "http://cgit.freedesktop.org/xorg/lib/libpciaccess/"
@@ -36,15 +36,3 @@ class Libpciaccess(Package):
     depends_on('libtool', type='build')
     depends_on('pkg-config@0.9.0:', type='build')
     depends_on('util-macros', type='build')
-
-    def install(self, spec, prefix):
-        # libpciaccess does not support OS X
-        if spec.satisfies('platform=darwin'):
-            # create a dummy directory
-            mkdir(prefix.lib)
-            return
-
-        configure('--prefix={0}'.format(prefix))
-
-        make()
-        make('install')