CI: switch to building against styhead branches where possible

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

ci/base.yml

@@ -7,7 +7,7 @@ distro: poky
 
 defaults:
   repos:
-    branch: master
+    branch: styhead
 
 repos:
   meta-arm:

ci/clang.yml

@@ -6,6 +6,7 @@ header:
 repos:
   meta-clang:
     url: https://github.com/kraj/meta-clang
+    branch: master
 
 local_conf_header:
   toolchain: |

ci/meta-secure-core.yml

@@ -6,6 +6,7 @@ header:
 repos:
   meta-secure-core:
     url: https://github.com/Wind-River/meta-secure-core.git
+    branch: master
     layers:
       meta-secure-core-common:
       meta-signing-key:

ci/meta-virtualization.yml

@@ -8,3 +8,4 @@ header:
 repos:
   meta-virtualization:
     url: https://git.yoctoproject.org/meta-virtualization
+    branch: master