better setup for asn1c

- use OAI location to retrieve asn1c
- use a specific commit instead of a branch name

cmake_targets/tools/build_helper

@@ -678,9 +678,12 @@ install_asn1c_from_source(){
     (
     $SUDO rm -rf /tmp/asn1c
     # GIT_SSL_NO_VERIFY=true git clone https://gitlab.eurecom.fr/oai/asn1c.git /tmp/asn1c
-    git clone https://github.com/brchiu/asn1c /tmp/asn1c
+    git clone https://gitlab.eurecom.fr/oai/asn1c.git /tmp/asn1c
     cd /tmp/asn1c
-    git checkout velichkov_s1ap_plus_option_group
+    # better to use a given commit than a branch in case the branch
+    # is updated and requires modifications in the source of OAI
+    #git checkout velichkov_s1ap_plus_option_group
+    git checkout ec830d70bbb014b769810355a2f321a91ccd8a58
     autoreconf -iv
     ./configure
     make -j`nproc`