Use -fsanitize=undefined when running tests with clang

tests/SConstruct

@@ -33,13 +33,16 @@ env.Append(PROTOCPATH = '#../generator')
 
 # Check the compilation environment, unless we are just cleaning up.
 if not env.GetOption('clean'):
-    def check_ccflags(context, flags):
+    def check_ccflags(context, flags, linkflags = ''):
         '''Check if given CCFLAGS are supported'''
         context.Message('Checking support for CCFLAGS="%s"... ' % flags)
         oldflags = context.env['CCFLAGS']
+        oldlinkflags = context.env['CCFLAGS']
         context.env.Append(CCFLAGS = flags)
+        context.env.Append(LINKFLAGS = linkflags)
         result = context.TryCompile("int main() {return 0;}", '.c')
         context.env.Replace(CCFLAGS = oldflags)
+        context.env.Replace(LINKFLAGS = oldlinkflags)
         context.Result(result)
         return result
     
@@ -83,6 +86,13 @@ if not env.GetOption('clean'):
         if conf.CheckCCFLAGS(extra):
             conf.env.Append(CORECFLAGS = extra)
     
+    # Check if we can use undefined behaviour sanitizer (only with clang)
+    extra = '-fsanitize=undefined '
+    if 'clang' in env['CC']:
+        if conf.CheckCCFLAGS(extra, linkflags = extra):
+            conf.env.Append(CORECFLAGS = extra)
+            conf.env.Append(LINKFLAGS = extra)
+    
     # End the config stuff
     env = conf.Finish()
 
@@ -119,9 +129,9 @@ elif 'tcc' in env['CC']:
 
 env.SetDefault(CORECFLAGS = '')
 
-if 'clang++' in env['CXX']:
+if 'clang' in env['CXX']:
     env.Append(CXXFLAGS = '-g -O0 -Wall -Werror -Wextra -Wno-missing-field-initializers')
-elif 'g++' in env['CXX']:
+elif 'g++' in env['CXX'] or 'gcc' in env['CXX']:
     env.Append(CXXFLAGS = '-g -O0 -Wall -Werror -Wextra -Wno-missing-field-initializers')
 elif 'cl' in env['CXX']:
     env.Append(CXXFLAGS = '/Zi /W2 /WX')