Enable -Werror by default for git builds on Linux hosts

Additional hosts can be added to the white list as they are confirmed to build
with --enable-werror.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

configure

@@ -356,11 +356,7 @@ else
 fi
 [ -f "$workdir/vl.c" ] || source_path_used="yes"
 
-werror="no"
+werror=""
-# generate compile errors on warnings for development builds
-#if grep cvs $source_path/VERSION > /dev/null 2>&1 ; then
-#werror="yes";
-#fi
 
 for opt do
   optarg=`expr "x$opt" : 'x[^=]*=\(.*\)'`
@@ -657,6 +653,18 @@ if test ! -x "$(which cgcc 2>/dev/null)"; then
     sparse="no"
 fi
 
+# Consult white-list to determine whether to enable werror
+# by default.  Only enable by default for git builds
+if test -z "$werror" ; then
+    z_version=`cut -f3 -d. $source_path/VERSION`
+    if test "$z_version" = "50" -a \
+       "$linux" = "yes" ; then
+	werror="yes"
+    else
+	werror="no"
+    fi
+fi
+
 #
 # Solaris specific configure tool chain decisions
 #