This patch fixes a bug where board-emerged aarch64 versions of GDB fail to
build with the error:

ld.lld: error: undefined symbol: set_tdesc_osabi(target_desc*, char const*)
referenced by aarch64.c:50

This fix should go into upstream GDB, but until it does we are fixing it here.
Author: cmtice@google.com
Date: 18-Nov-2020

diff --git a/gdb/arch/aarch64.c b/gdb/arch/aarch64.c
index 4a23c13..4be3c43 100644
--- a/gdb/arch/aarch64.c
+++ b/gdb/arch/aarch64.c
@@ -33,6 +33,8 @@ aarch64_create_target_description (uint64_t vq, bool pauth_p)
 
 #ifndef IN_PROCESS_AGENT
   set_tdesc_architecture (tdesc, "aarch64");
+
+  set_tdesc_osabi (tdesc, "GNU/Linux");
 #endif
 
   long regnum = 0;
@@ -47,7 +49,5 @@ aarch64_create_target_description (uint64_t vq, bool pauth_p)
   if (pauth_p)
     regnum = create_feature_aarch64_pauth (tdesc, regnum);
 
-  set_tdesc_osabi (tdesc, "GNU/Linux");
-
   return tdesc;
 }