Merge #20346: script: modify security-check.py to use "==" instead of "is" for literal comparison

b6121edf70 swapped "is" for "==" in literal comparison (Tyler Chambers)

Pull request description:

  In Python 3.8+ literal comparisons using "is" instead of "==" produce a SyntaxWarning [source](https://docs.python.org/3.8/whatsnew/3.8.html#changes-in-python-behavior).

  I checked the entire devtools directory, this seems to be the only occurrence.

  This is a small fix, but removes the SyntaxWarning.
  Fixes: #20338

ACKs for top commit:
  hebasto:
    re-ACK b6121edf70, only squashed since my [previous](https://github.com/bitcoin/bitcoin/pull/20346#pullrequestreview-525934568) review.
  practicalswift:
    re-ACK b6121edf70: patch still looks correct
  theStack:
    utACK b6121edf70

Tree-SHA512: 82a43495d6552fbaa3b02b58f0930b049d27aa937fe44b47714e3c059f844cc494de20674557371cbccf24fb8873ecb7376fb965ae326847eed2b855ed2d59c6

contrib/devtools/security-check.py

@@ -62,7 +62,7 @@ def get_ELF_program_headers(executable):
                     splitline = [x.strip() for x in line.split()]
                     flags = splitline[ofs_flags]
                     # check for 'R', ' E'
-                    if splitline[ofs_flags + 1] is 'E':
+                    if splitline[ofs_flags + 1] == 'E':
                         flags += ' E'
                     headers.append((typ, flags, []))
             count += 1