TCG: add wasm backend

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

configure

@@ -340,7 +340,9 @@ int main(void) { return 0; }
 EOF
 }
 
-if check_define __linux__ ; then
+if check_define __EMSCRIPTEN__ ; then
+  host_os=linux
+elif check_define __linux__ ; then
   host_os=linux
 elif check_define _WIN32 ; then
   host_os=windows
@@ -526,6 +528,10 @@ case "$cpu" in
     linux_arch=x86
     CPU_CFLAGS="-m64"
     ;;
+  wasm32)
+    host_arch=wasm32
+    CPU_CFLAGS="-m32"
+    ;;
 esac
 
 # Now we have our CPU_CFLAGS we can check if we are targeting a 32 or