base: Use system libelf instead of ext

The only change needed is to remove EM_SPARC64, which from what I can
tell was removed from elf.h in 1998.

https://sources.debian.org/src/glibc/2.24-11+deb9u1/ChangeLog.8/#L6134

Change-Id: I0dd7e23ea44b19c2ebd9c6eff7cbaedfe69d821b
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/33317
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Gabe Black <gabeblack@google.com>

SConstruct

@@ -748,6 +748,10 @@ if not conf.CheckLibWithHeader('z', 'zlib.h', 'C++','zlibVersion();'):
           'and/or zlib.h header file.\n'
           'Please install zlib and try again.')
 
+if not conf.CheckLibWithHeader('elf', 'gelf.h', 'C++',
+                               'elf_version(EV_CURRENT);'):
+    error('Did not find ELF access library libelf')
+
 # If we have the protobuf compiler, also make sure we have the
 # development libraries. If the check passes, libprotobuf will be
 # automatically added to the LIBS environment variable. After