Set lld as the default linker for Clang builds

The LLVM linker replaces the GNU linker as default for the link on Clang
builds. It is possible to override the default linker by setting the LD build
flag.

The patch also updates the TF-A doc.

Change-Id: Ic08552b9994d4fa8f0d4863e67a2726c1dce2e35
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
diff --git a/docs/getting_started/initial-build.rst b/docs/getting_started/initial-build.rst
index 893aba2..d4a8f01 100644
--- a/docs/getting_started/initial-build.rst
+++ b/docs/getting_started/initial-build.rst
@@ -18,9 +18,10 @@
 
    It is possible to build TF-A using Clang or Arm Compiler 6. To do so
    ``CC`` needs to point to the clang or armclang binary, which will
-   also select the clang or armclang assembler. Be aware that the
-   GNU linker is used by default.  In case of being needed the linker
-   can be overridden using the ``LD`` variable. Clang linker version 6 is
+   also select the clang or armclang assembler. Be aware that for Arm Compiler,
+   the GNU linker is used by default. However for Clang LLVM linker (LLD)
+   is used by default. In case of being needed the linker can be overridden
+   using the ``LD`` variable. LLVM linker (LLD) version 9 is
    known to work with TF-A.
 
    In both cases ``CROSS_COMPILE`` should be set as described above.
@@ -114,4 +115,4 @@
 
 --------------
 
-*Copyright (c) 2019, Arm Limited. All rights reserved.*
+*Copyright (c) 2020, Arm Limited. All rights reserved.*