testlist: Enable cxxtest build on sim

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
diff --git a/testlist/all.dat b/testlist/all.dat
index 8bc56ee..d9ccf21 100644
--- a/testlist/all.dat
+++ b/testlist/all.dat
@@ -23,7 +23,6 @@
 -nr5m100-nexys4:nsh
 
 /sim
--sim:cxxtest
 
 /x86
 
diff --git a/testlist/sim.dat b/testlist/sim.dat
index 44bdd19..18a3d6d 100644
--- a/testlist/sim.dat
+++ b/testlist/sim.dat
@@ -1,5 +1,5 @@
 /sim
--sim:cxxtest
+-Darwin,sim:cxxtest
 
 # CONFIG_SIM_M32=y
 # The recent versions of macOS is 64-bit only