scons: Remove -Werror for the gem5 v22.0 release

While gem5 compiles on all our supported compilers, removing the -Werror
flag on the stable branch ensures that, as new compilers are released
with stricter warnings, gem5 remains compilable.

Change-Id: I0efe6cf83714720ae0d5de9de9b993c6d8ab00a8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/60510
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

SConstruct

@@ -418,13 +418,6 @@ for variant_path in variant_paths:
                     conf.CheckLinkFlag(
                             '-Wl,--thread-count=%d' % GetOption('num_jobs'))
 
-        # Treat warnings as errors but white list some warnings that we
-        # want to allow (e.g., deprecation warnings).
-        env.Append(CCFLAGS=['-Werror',
-                             '-Wno-error=deprecated-declarations',
-                             '-Wno-error=deprecated',
-                            ])
-
     else:
         error('\n'.join((
               "Don't know what compiler options to use for your compiler.",