Bzip2 now uses 'spack_cc' as a compiler, instead of plain 'cc' (#7074)

Looking at build logs, it seems that prior to this commit bzip2 was
using 'cc', and relying on the PATH to be set correctly to find Spack
wrappers. This commit improves the robustness of the recipe, by using
the absolute path of the wrapper.

var/spack/repos/builtin/packages/bzip2/package.py

@@ -51,8 +51,10 @@ def libs(self):
     def patch(self):
         # bzip2 comes with two separate Makefiles for static and dynamic builds
         # Tell both to use Spack's compiler wrapper instead of GCC
-        filter_file(r'^CC=gcc', 'CC=cc', 'Makefile')
-        filter_file(r'^CC=gcc', 'CC=cc', 'Makefile-libbz2_so')
+        filter_file(r'^CC=gcc', 'CC={0}'.format(spack_cc), 'Makefile')
+        filter_file(
+            r'^CC=gcc', 'CC={0}'.format(spack_cc), 'Makefile-libbz2_so'
+        )
 
         # The Makefiles use GCC flags that are incompatible with PGI
         if self.compiler.name == 'pgi':