Let packages call use_cray_compilers() in install to get , etc set to cray names

lib/spack/env/cc

@@ -110,13 +110,13 @@ case "$command" in
         comp="CXX"
         lang_flags=CXX
         ;;
-    f90|fc|f95|gfortran|ifort|pgfortran|xlf90|nagfor)
+    ftn|f90|fc|f95|gfortran|ifort|pgfortran|xlf90|nagfor)
         command="$SPACK_FC"
         language="Fortran 90"
         comp="FC"
         lang_flags=F
         ;;
-    f77|gfortran|ifort|pgfortran|xlf|nagfor)
+    f77|gfortran|ifort|pgfortran|xlf|nagfor|ftn)
         command="$SPACK_F77"
         language="Fortran 77"
         comp="F77"

lib/spack/env/craype/CC

@@ -0,0 +1 @@
+../cc

lib/spack/env/craype/cc

@@ -0,0 +1 @@
+../cc

lib/spack/env/craype/ftn

@@ -0,0 +1 @@
+../cc

lib/spack/spack/package.py

@@ -1439,6 +1439,13 @@ def install_dependency_symlinks(pkg, spec, prefix):
     flatten_dependencies(spec, prefix)
 
 
+def use_cray_compiler_names():
+    """Compiler names for builds that rely on cray compiler names."""
+    os.environ['CC'] = 'cc'
+    os.environ['CXX'] = 'CC'
+    os.environ['FC'] = 'ftn'
+    os.environ['F77'] = 'ftn'
+
 def flatten_dependencies(spec, flat_dir):
     """Make each dependency of spec present in dir via symlink."""
     for dep in spec.traverse(root=False):