chrpath: do less work

Instead of trying to change the RPATH in every file under the binary
directories, check that the file is an ELF first.

This means that we don't attempt to change the RPATH on the entire
Python standard library, for example.

Also return early if the directory to iterate doesn't exist.

(From OE-Core rev: 977f4baacf7c8d06d9cfe5c5e39bb8bc19f27028)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/chrpath.bbclass

@@ -2,7 +2,13 @@ CHRPATH_BIN ?= "chrpath"
 PREPROCESS_RELOCATE_DIRS ?= ""
 
 def process_file_linux(cmd, fpath, rootdir, baseprefix, tmpdir, d, break_hardlinks = False):
-    import subprocess as sub
+    import subprocess as sub, oe.qa
+
+    with oe.qa.ELFFile(fpath) as elf:
+        try:
+            elf.open()
+        except oe.qa.NotELFFileError:
+            return
 
     p = sub.Popen([cmd, '-l', fpath],stdout=sub.PIPE,stderr=sub.PIPE)
     out, err = p.communicate()
@@ -72,6 +78,10 @@ def process_file_darwin(cmd, fpath, rootdir, baseprefix, tmpdir, d, break_hardli
         out, err = p.communicate()
 
 def process_dir(rootdir, directory, d, break_hardlinks = False):
+    bb.debug(2, "Checking %s for binaries to process" % directory)
+    if not os.path.exists(directory):
+        return
+
     import stat
 
     rootdir = os.path.normpath(rootdir)
@@ -80,10 +90,6 @@ def process_dir(rootdir, directory, d, break_hardlinks = False):
     baseprefix = os.path.normpath(d.expand('${base_prefix}'))
     hostos = d.getVar("HOST_OS")
 
-    #bb.debug("Checking %s for binaries to process" % directory)
-    if not os.path.exists(directory):
-        return
-
     if "linux" in hostos:
         process_file = process_file_linux
     elif "darwin" in hostos: