builds: Set CFLAGS += -Werror in all linux subdirectory compilations

scripts/github_dist.sh

@@ -17,7 +17,7 @@ if test $err = 0 -a "x$ARCHIVE" != "x"; then
     DIR=`pwd`/`tar taf $ARCHIVE |cut -d/ -f1|head -1`
     tar xaf $ARCHIVE && cd $DIR && \
         $DIR/configure $PREFIX --enable-tests  --enable-silent-rules --enable-documentation --enable-examples --disable-dtls && \
-        make && make install
+        make EXTRA_CFLAGS=-Werror && make install EXTRA_CFLAGS=-Werror
     err=$?
 fi