Build-CI: Use 'stable' spack version in manifests

Author: dougiesquire

.github/build-ci/manifests/gcc.spack.yaml.j2

@@ -1,7 +1,7 @@
 spack:
   specs:
   # *_compiler is defined in the .github/build-ci/data/standard.json file
-  - access-mocsy@git.{{ ref }}
+  - access-mocsy@git.{{ ref }}=stable
   packages:
     gcc:
       require:

.github/build-ci/manifests/intel.spack.yaml.j2

@@ -1,7 +1,7 @@
 spack:
   specs:
   # *_compiler is defined in the .github/build-ci/data/standard.json file
-  - access-mocsy@git.{{ ref }}
+  - access-mocsy@git.{{ ref }}=stable
   packages:
     intel-oneapi-compiler-classic:
       require:

.github/build-ci/manifests/oneapi.spack.yaml.j2

@@ -1,7 +1,7 @@
 spack:
   specs:
   # *_compiler is defined in the .github/build-ci/data/standard.json file
-  - access-mocsy@git.{{ ref }}
+  - access-mocsy@git.{{ ref }}=stable
   packages:
     intel-oneapi-compilers:
       require: