scons: Reading SConscript files ...
Package libelf was not found in the pkg-config search path.
Perhaps you should add the directory containing `libelf.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libelf' found
OSError: 'pkg-config --cflags libelf' exited 1:
  File "/home/jd/eth32/eth32nix_rc2/SConstruct", line 23:
    env.MergeFlags('!pkg-config --cflags libelf')
  File "/usr/lib/scons-0.97/SCons/Environment.py", line 662:
    args = self.ParseFlags(args)
  File "/usr/lib/scons-0.97/SCons/Environment.py", line 651:
    do_parse(arg, do_parse)
  File "/usr/lib/scons-0.97/SCons/Environment.py", line 537:
    arg = self.backtick(arg[1:])
  File "/usr/lib/scons-0.97/SCons/Environment.py", line 473:
    raise OSError("'%s' exited %d" % (command, status))