[build] makepchinput.py should not collect PCH input headers from roottest:

This fixed 19 sporadic errors seen in the incrementals:
    projectroot.roottest.root.collection.roottest_root_collection_execMissing
    projectroot.roottest.root.meta.roottest_root_meta_drawing
    projectroot.roottest.root.meta.roottest_root_meta_runautoload_auto
    projectroot.roottest.root.io.fakeClass.roottest_root_io_fakeClass_make
    projectroot.roottest.root.tree.split.roottest_root_tree_split_make
    projectroot.roottest.root.tree.selector.roottest_root_tree_selector_make
    projectroot.roottest.root.treeformula.sync.roottest_root_treeformula_sync_make
    projectroot.roottest.root.treeformula.parse.roottest_root_treeformula_parse_make
    projectroot.roottest.root.treeformula.retobj.roottest_root_treeformula_retobj_make
    projectroot.roottest.root.treeformula.schemaEvolution.roottest_root_treeformula_schemaEvolution_make
    projectroot.roottest.root.tree.addresses.roottest_root_tree_addresses_make
    projectroot.roottest.root.treeproxy.roottest_root_treeproxy_make
    projectroot.roottest.root.tree.evolution.roottest_root_tree_evolution_make
    projectroot.roottest.root.treeformula.array.roottest_root_treeformula_array_make
    projectroot.roottest.root.meta.tclass.roottest_root_meta_tclass_execState
    projectroot.roottest.root.io.evolution.roottest_root_io_evolution_make
    projectroot.roottest.root.io.datamodelevolution.roottest_root_io_datamodelevolution_make
    projectroot.test.test_stresstmva_interpreted
    projectroot.roottest.root.tree.friend.roottest_root_tree_friend_make
Caused by having roottest/root/tree/cache/Event.h in the PCH.
It ended up there since 6aa6e3e85bda2b3474eb46f38cb857e718c838cd in roottest, which renamed the
dictionary from roottest/root/tree/cache/ to match the search pattern of makepchinput.py.

build/unix/makepchinput.py

@@ -192,7 +192,7 @@ def getDictNames(theDirName):
    allDictNames = []
    for wildcard in wildcards:
       allDictNames += glob.glob(wildcard)
-   stdDictpattern = os.path.join("core","metautils","src","G__std_")
+   stdDictpattern = os.path.join("core","metautils","src","G__std_", "roottest")
    dictNames = filter (lambda dictName: not (stdDictpattern in dictName),allDictNames )
    return dictNames