Third attempt to invoke create_config properly

Second attempt failed due to $_ not being standard and as such it's
interpretation by certain shells when they were symlinked to /bin/sh
and invoked as such led to unpredictable results. So instead of trying
to be clever just use /bin/sh directly (That's what direct execution
would have led to anyway)

Hopefully this time nothing will break (Mingw?)

Thanks to Jordan Justen for report and analysis.
[Previous attempt (THISSHELL one) deserves a credit but reporter is
 too humble]
Signed-off-by: Nmalc <av1474@comtv.ru>

configure

@@ -15,8 +15,6 @@ TMPC="${TMPDIR1}/qemu-conf-${RANDOM}-$$-${RANDOM}.c"
 TMPO="${TMPDIR1}/qemu-conf-${RANDOM}-$$-${RANDOM}.o"
 TMPE="${TMPDIR1}/qemu-conf-${RANDOM}-$$-${RANDOM}"
 
-THISSHELL=${_:-/bin/sh}
-
 trap "rm -f $TMPC $TMPO $TMPE ; exit" 0 2 3 15
 
 compile_object() {
@@ -1797,7 +1795,7 @@ echo "EXESUF=$EXESUF" >> $config_host_mak
 
 echo "/* Automatically generated by configure - do not modify */" > $config_host_h
 
-$THISSHELL $source_path/create_config < $config_host_mak >> $config_host_h
+/bin/sh $source_path/create_config < $config_host_mak >> $config_host_h
 
 if test -f ${config_host_h}~ ; then
   if cmp -s $config_host_h ${config_host_h}~ ; then
@@ -2217,7 +2215,7 @@ echo "QEMU_CFLAGS+=$cflags" >> $config_mak
 echo "/* Automatically generated by configure - do not modify */" > $config_h
 echo "#include \"../config-host.h\"" >> $config_h
 
-$THISSHELL $source_path/create_config < $config_mak >> $config_h
+/bin/sh $source_path/create_config < $config_mak >> $config_h
 
 if test -f ${config_h}~ ; then
   if cmp -s $config_h ${config_h}~ ; then