SCons: add `methods.using_clang` to check used compiler

Also rename `use_gcc` to `using_gcc` to make it clear that it returns
a config but does not alter it.

(cherry picked from commit e4a96164b6)

SConstruct

@@ -341,7 +341,7 @@ if selected_platform in platform_list:
         shadow_local_warning = []
         all_plus_warnings = ['-Wwrite-strings']
 
-        if methods.use_gcc(env):
+        if methods.using_gcc(env):
             version = methods.get_compiler_version(env)
             if version != None and version[0] >= '7':
                 shadow_local_warning = ['-Wshadow-local']
@@ -349,7 +349,7 @@ if selected_platform in platform_list:
             # FIXME: enable -Wimplicit-fallthrough once #26135 is fixed
             # FIXME: enable -Wclobbered once #26351 is fixed
             env.Append(CCFLAGS=['-Wall', '-Wextra', '-Wno-implicit-fallthrough', '-Wno-unused-parameter'] + all_plus_warnings + shadow_local_warning)
-            if methods.use_gcc(env):
+            if methods.using_gcc(env):
                 env['CCFLAGS'] += ['-Wno-clobbered']
 
         elif (env["warnings"] == 'all'):

methods.py

@@ -668,5 +668,8 @@ def get_compiler_version(env):
     else:
         return None
 
-def use_gcc(env):
+def using_gcc(env):
     return 'gcc' in os.path.basename(env["CC"])
+
+def using_clang(env):
+    return 'clang' in os.path.basename(env["CC"])

platform/server/detect.py

@@ -1,7 +1,6 @@
 import os
 import platform
 import sys
-from methods import get_compiler_version, use_gcc
 
 # This file is mostly based on platform/x11/detect.py.
 # If editing this file, make sure to apply relevant changes here too.

platform/x11/detect.py

@@ -2,7 +2,7 @@ import os
 import platform
 import sys
 from compat import decode_utf8
-from methods import get_compiler_version, use_gcc
+from methods import get_compiler_version, using_gcc
 
 def is_active():
     return True
@@ -160,7 +160,7 @@ def configure(env):
     env.Append(LINKFLAGS=['-pipe'])
 
     # Check for gcc version >= 6 before adding -no-pie
-    if use_gcc(env):
+    if using_gcc(env):
         version = get_compiler_version(env)
         if version != None and version[0] >= '6':
             env.Append(CCFLAGS=['-fpie'])