ci: Fix overriding OPTS provided from the yml.

For GCC builds we're overriding --disable-ssl or --enable-shared
options set up in the GHA yml file.

Fix that by adding to EXTRA_OPTS instead.

Fixes: 2581b0ad11 ("travis: Combine kernel builds.")
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

.ci/linux-build.sh

@@ -221,7 +221,7 @@ elif [ "$M32" ]; then
     # difference on 'configure' and 'make' stages.
     export CC="$CC -m32"
 else
-    OPTS="--enable-sparse"
+    EXTRA_OPTS="$EXTRA_OPTS --enable-sparse"
     if [ "$AFXDP" ]; then
         # netdev-afxdp uses memset for 64M for umem initialization.
         SPARSE_FLAGS="${SPARSE_FLAGS} -Wno-memcpy-max-count"