lua: fix compilation on Cray (#16713)

Problem: when calling `static_to_shared_library` on the `cray` arch, it
produces a non-sensical compiler command with no input files.  For
example, when installing lua@5.2.4, it produced:
'gcc -lm -ldl -o /big-long-spack-path/liblua.so.5.2.4'

Solution: do the same thing on `cray` that is done for `linux`

lib/spack/spack/build_environment.py

@@ -538,7 +538,7 @@ def _static_to_shared_library(arch, compiler, static_lib, shared_lib=None,
 
     # TODO: Compiler arguments should not be hardcoded but provided by
     #       the different compiler classes.
-    if 'linux' in arch:
+    if 'linux' in arch or 'cray' in arch:
         soname = os.path.basename(shared_lib)
 
         if compat_version: