In order to have a working pldd, we need to backport this upstream commit:

commit 1a4c27355e146b6d8cc6487b998462c7fdd1048f
Author: Adhemerval Zanella <adhemerval.zanella>
Date:   Thu Apr 11 18:12:00 2019 -0300

    elf: Fix pldd (BZ#18035)
    
    Since 9182aa67994 (Fix vDSO l_name for GDB's, BZ#387) the initial link_map
    for executable itself and loader will have both l_name and l_libname->name
    holding the same value due:
    
     elf/dl-object.c
    
     95   new->l_name = *realname ? realname : (char *) newname->name + libname_len - 1;
    
    Since newname->name points to new->l_libname->name.
    
    This leads to pldd to an infinite call at:
    
     elf/pldd-xx.c

The test depends on <support/subprocess.h> from this commit:

commit 0e169691290a6d2187a4ff41495fc5678cbfdcdc
Author: Adhemerval Zanella <adhemerval.zanella>
Date:   Fri Apr 12 17:39:53 2019 -0300

    support: Add support_capture_subprogram
    
    Its API is similar to support_capture_subprocess, but rather creates a
    new process based on the input path and arguments.  Under the hoods it
    uses posix_spawn to create the new process.
    
    It also allows the use of other support_capture_* functions to check
    for expected results and free the resources.