Merge #15244: gdb attaching to process during tests has non-sudo solution

f96dbd1 gdb attaching to process during tests has non-sudo solution (Gregory Sanders)

Pull request description:

  There are some security considerations, so a link is attached.

Tree-SHA512: 67dd9c4b26b1e6d8e9a9fe766d309c0af69b752f6f544f3dce4bdcc95ae85feb9a49ac600c3f70d100629505d2340ab43932ded53b1485f80b97981e6df6a527

Author: laanwj

test/README.md

@@ -175,7 +175,8 @@ cat /tmp/user/1000/testo9vsdjo3/node1/regtest/bitcoind.pid
 gdb /home/example/bitcoind <pid>
 ```
 
-Note: gdb attach step may require `sudo`
+Note: gdb attach step may require ptrace_scope to be modified, or `sudo` preceding the `gdb`.
+See this link for considerations: https://www.kernel.org/doc/Documentation/security/Yama.txt
 
 ### Util tests