CheckerCPU: Make CheckerCPU runtime selectable instead of compile selectable

Enables the CheckerCPU to be selected at runtime with the --checker option
from the configs/example/fs.py and configs/example/se.py configuration
files.  Also merges with the SE/FS changes.

src/cpu/SConscript

@@ -69,10 +69,8 @@ virtual Fault completeAcc(uint8_t *data, %s *xc, Trace::InstRecord *traceData) c
 # it's enabled.  This isn't used for anything else other than StaticInst
 # headers.
 temp_cpu_list = env['CPU_MODELS'][:]
-
-if env['USE_CHECKER']:
-    temp_cpu_list.append('CheckerCPU')
-    SimObject('CheckerCPU.py')
+temp_cpu_list.append('CheckerCPU')
+SimObject('CheckerCPU.py')
 
 # Generate header.
 def gen_cpu_exec_signatures(target, source, env):
@@ -98,13 +96,8 @@ env.Command('static_inst_exec_sigs.hh', (),
             Action(gen_cpu_exec_signatures, gen_sigs_string,
                    varlist = temp_cpu_list))
 
-env.Depends('static_inst_exec_sigs.hh', Value(env['USE_CHECKER']))
 env.Depends('static_inst_exec_sigs.hh', Value(env['CPU_MODELS']))
 
-# List of suppported CPUs by the Checker.  Errors out if USE_CHECKER=True
-# and one of these are not being used.
-CheckerSupportedCPUList = ['O3CPU', 'OzoneCPU']
-
 SimObject('BaseCPU.py')
 SimObject('FuncUnit.py')
 SimObject('ExeTracer.py')
@@ -133,21 +126,10 @@ if env['TARGET_ISA'] == 'sparc':
     SimObject('LegionTrace.py')
     Source('legiontrace.cc')
 
-if env['USE_CHECKER']:
-    SimObject('DummyChecker.py')
-    Source('checker/cpu.cc')
-    Source('dummy_checker_builder.cc')
-    DebugFlag('Checker')
-    checker_supports = False
-    for i in CheckerSupportedCPUList:
-        if i in env['CPU_MODELS']:
-            checker_supports = True
-    if not checker_supports:
-        print "Checker only supports CPU models",
-        for i in CheckerSupportedCPUList:
-            print i,
-        print ", please set USE_CHECKER=False or use one of those CPU models"
-        Exit(1)
+SimObject('DummyChecker.py')
+Source('checker/cpu.cc')
+Source('dummy_checker_builder.cc')
+DebugFlag('Checker')
 
 DebugFlag('Activity')
 DebugFlag('Commit')