help menu updated in document for native architecture.

Compilation steps corrected on Ubuntu 20.
Signed-off-by: Manish <Manish1.Kumar@amd.com>

doc/BUILD.md

@@ -193,6 +193,7 @@ Using the help option of the build script you can get the list of available opti
 | --UE                                                        | maintained and tested in CI                 | build `lte-uesoftmodem` the LTE UE                           |
 | --gNB                                                       | maintained and tested in CI                 | build `nr-softmodem` the 5G gNodeB                           |
 | --nrUE                                                      | maintained and tested in CI                 | build `nr-uesoftmodem` the 5G UE                             |
+| --arch-native                                               | maintained                                  | build with native architecture optimization                  |
 | --usrp-recplay                                              | deprecated                                  | use the USRP configuration parameters to use the record player. |
 | --build-lib                                                 | maintained                                  | build  optional shared library(ies), which can then be loaded at run time via command line option. Use the --help option to get the list of supported optional libraries. `all` can be used to build all available optional libraries. |
 | --UE-conf-nvram                                             | maintained                                  | Specifies the path to the input file used by the conf2uedata utility. defaults to [openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf](../openair3/NAS/TOOLS/ue_eurecom_test_sfr.conf) |

doc/TESTING_5GSA_setup.md

@@ -82,15 +82,7 @@ To get the code and build the gNB executable:
     git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git
     git checkout develop
     
-    # Install dependencies in Ubuntu 20.04
-    cd
-    cd openairinterface5g/
-    source oaienv
-    cd cmake_targets/
-    ./install_external_packages.ubuntu20
-    
     # Build OAI gNB
-    cd
     cd openairinterface5g/
     source oaienv
     cd cmake_targets/