BLD: compile with default c++98 language standard

Ignore language option in CXXFLAGS environment variable.

Author: pavoljuhas

conda-recipe/sconscript.local

@@ -11,6 +11,10 @@ env.MergeFlags(os.environ['CPPFLAGS'])
 env.MergeFlags(os.environ['CXXFLAGS'])
 env.MergeFlags(os.environ['LDFLAGS'])
 
+# Use the default c++98 language standard
+cxxflags98 = [f for f in env['CXXFLAGS'] if not f.startswith('-std=')]
+env.Replace(CXXFLAGS=cxxflags98)
+
 # Silence copious warnings from the boost headers.
 P = os.environ['PREFIX']
 env.Prepend(CCFLAGS=['-isystem{}/include'.format(P)])