Add Compiler configuration in spack.yaml

spack.yaml

@@ -44,3 +44,17 @@ spack:
     all:
       compiler: [gcc]
   view: /usr/local
+  compilers::
+  - compiler:
+      spec: gcc@11.2.0
+      paths:
+        cc: /usr/bin/gcc
+        cxx: /usr/bin/g++
+        f77: /usr/bin/gfortran
+        fc: /usr/bin/gfortran
+      flags: {}
+      operating_system: ubuntu18.04
+      target: x86_64
+      modules: []
+      environment: {}
+      extra_rpaths: []