build: fix clang detection on FreeBSD

configure.ac

@@ -113,7 +113,7 @@ AC_ARG_ENABLE([fastparser],
 AX_CC_CLANG
 AS_IF([test "$enable_fastparser" = "yes"],[
     AS_IF([test -n "$CC_CLANG_VERSION"],[
-       clang_vernum=$(printf "%02d%02d%02d" $(tr "." " " <<< "$CC_CLANG_VERSION"))
+      clang_vernum=$(printf "%02d%02d%02d" $(echo "$CC_CLANG_VERSION" | tr "." " "))
       AS_IF([test $clang_vernum -lt 030900],[
         AC_MSG_WARN([Fast parser disabled due to a compiler bug, see https://llvm.org/bugs/show_bug.cgi?id=23490])
         enable_fastparser=no