mhshow/test-charset: Test iconv(1)'s result, not just its exit status.

Problems with generating the input to iconv(1) were hidden as long as it
could be converted from EBCDIC-US to UTF-8 because only the exit status
was tested.  Check the output is as expected too.

diff --git a/test/mhshow/test-charset b/test/mhshow/test-charset
index 72aeb79..8f19967 100755 (executable)
--- a/test/mhshow/test-charset
+++ b/test/mhshow/test-charset
@@ -29,7 +29,8 @@ else
     #### FreeBSD10 buildbot.  It doesn't support EBCDIC-US, which is used
     #### by the checks, so check for that.  Though that doesn't seem to be
     #### the reason.
     #### FreeBSD10 buildbot.  It doesn't support EBCDIC-US, which is used
     #### by the checks, so check for that.  Though that doesn't seem to be
     #### the reason.

-    printf '\344' | iconv -f EBCDIC-US -t UTF-8 >/dev/null 2>&1  ||
+    utf8="`printf '\344' | iconv -f EBCDIC-US -t UTF-8 2>/dev/null`" &&
+    test x"$utf8" = xU ||

         skip_param_value_checks=1
 fi
 
         skip_param_value_checks=1
 fi