scons: Turn a lot of compiler flag vars into env vars.

These are used to adapt gem5 to the system it's being built on, and so
should be attached to the host via the environment rather than gem5's
configuration.

Change-Id: I2adfe1af484dcdeae32a48097d9aa87752a7ed2a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/56752
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

SConstruct

@@ -253,13 +253,6 @@ global_vars_file = os.path.join(build_root, 'variables.global')
 global_vars = Variables(global_vars_file, args=ARGUMENTS)
 
 global_vars.AddVariables(
-    ('CCFLAGS_EXTRA', 'Extra C and C++ compiler flags', ''),
-    ('GEM5PY_CCFLAGS_EXTRA', 'Extra C and C++ gem5py compiler flags', ''),
-    ('GEM5PY_LINKFLAGS_EXTRA', 'Extra marshal gem5py flags', ''),
-    ('LINKFLAGS_EXTRA', 'Extra linker flags', ''),
-    ('PYTHON_CONFIG', 'Python config binary to use',
-     [ 'python3-config', 'python-config']
-    ),
     ('BATCH', 'Use batch pool for build and tests', False),
     ('BATCH_CMD', 'Batch pool submission command name', 'qdo'),
     ('M5_BUILD_CACHE', 'Cache built objects in this directory', False),

site_scons/gem5_scons/defaults.py

@@ -46,7 +46,9 @@ def EnvDefaults(env):
     # export TERM so that clang reports errors in color
     use_vars = set([ 'AS', 'AR', 'CC', 'CXX', 'HOME', 'LD_LIBRARY_PATH',
                      'LIBRARY_PATH', 'PATH', 'PKG_CONFIG_PATH', 'PROTOC',
-                     'PYTHONPATH', 'RANLIB', 'TERM' ])
+                     'PYTHONPATH', 'RANLIB', 'TERM', 'PYTHON_CONFIG',
+                     'CCFLAGS_EXTRA', 'GEM5PY_CCFLAGS_EXTRA',
+                     'GEM5PY_LINKFLAGS_EXTRA', 'LINKFLAGS_EXTRA'])
 
     use_prefixes = [
         "ASAN_",           # address sanitizer symbolizer path and settings
@@ -68,7 +70,12 @@ def EnvDefaults(env):
     var_overrides = {
         'CC': env['CC'],
         'CXX': env['CXX'],
-        'PROTOC': 'protoc'
+        'PROTOC': 'protoc',
+        'PYTHON_CONFIG': [ 'python3-config', 'python-config' ],
+        'CCFLAGS_EXTRA': '',
+        'GEM5PY_CCFLAGS_EXTRA': '',
+        'GEM5PY_LINKFLAGS_EXTRA': '',
+        'LINKFLAGS_EXTRA': '',
     }
     for key,default in var_overrides.items():
         env[key] = env['ENV'].get(key, default)