py-pythran: update checksum for patch (#25693)

* Replace URL patch with file patch
* Add comment explaining patch origin and purpose

var/spack/repos/builtin/packages/py-pythran/omp.patch

@@ -0,0 +1,70 @@
+diff --git a/omp/__init__.py b/omp/__init__.py
+index bddae3063..10a4cc995 100644
+--- a/omp/__init__.py
++++ b/omp/__init__.py
+@@ -69,10 +69,16 @@ class OpenMP(object):
+ 
+     def init_not_msvc(self):
+         """ Find OpenMP library and try to load if using ctype interface. """
+-        # find_library() does not search automatically LD_LIBRARY_PATH
++        # find_library() does not automatically search LD_LIBRARY_PATH
++        # until Python 3.6+, so we explicitly add it.
++        # LD_LIBRARY_PATH is used on Linux, while macOS uses DYLD_LIBRARY_PATH
++        # and DYLD_FALLBACK_LIBRARY_PATH.
+         paths = os.environ.get('LD_LIBRARY_PATH', '').split(':')
++        paths += os.environ.get('DYLD_LIBRARY_PATH', '').split(':')
++        paths += os.environ.get('DYLD_FALLBACK_LIBRARY_PATH', '').split(':')
+ 
+-        for libomp_name in self.get_libomp_names():
++        libomp_names = self.get_libomp_names()
++        for libomp_name in libomp_names:
+             if cxx is None or sys.platform == 'win32':
+                 # Note: Clang supports -print-file-name, but not yet for
+                 # clang-cl as of v12.0.0 (April '21)
+@@ -87,25 +93,27 @@ class OpenMP(object):
+             except (OSError, CalledProcessError):
+                 pass
+ 
+-        # Try to load find libgomp shared library using loader search dirs
+-        libgomp_path = find_library("gomp")
+-
+-        # Try to use custom paths if lookup failed
+-        for path in paths:
+-            if libgomp_path:
+-                break
+-            path = path.strip()
+-            if os.path.isdir(path):
+-                libgomp_path = find_library(os.path.join(str(path), "libgomp"))
+-
+-        if not libgomp_path:
+-            raise ImportError("I can't find a shared library for libgomp,"
+-                              " you may need to install it or adjust the "
+-                              "LD_LIBRARY_PATH environment variable.")
+-        else:
+-            # Load the library (shouldn't fail with an absolute path right?)
+-            self.libomp = ctypes.CDLL(libgomp_path)
+-            self.version = 45
++        for libomp_name in libomp_names:
++            # Try to load find libomp shared library using loader search dirs
++            libomp_path = find_library(libomp_name)
++
++            # Try to use custom paths if lookup failed
++            for path in paths:
++                if libomp_path:
++                    break
++                path = path.strip()
++                if os.path.isfile(os.path.join(path, libomp_name)):
++                    libomp_path = os.path.join(path, libomp_name)
++
++            if libomp_path:
++                # Load the library (shouldn't fail with an absolute path right?)
++                self.libomp = ctypes.CDLL(libomp_path)
++                self.version = 45
++                return
++
++        raise ImportError("I can't find a shared library for libomp,"
++                          " you may need to install it or adjust the "
++                          "LD_LIBRARY_PATH environment variable.")
+ 
+     def __getattr__(self, name):
+         """

var/spack/repos/builtin/packages/py-pythran/package.py

@@ -46,9 +46,8 @@ class PyPythran(PythonPackage):
     depends_on('py-beniget', when='@:0.9.3', type=('build', 'run'))
     depends_on('llvm-openmp', when='%apple-clang', type=('build', 'run'))
 
-    patch('https://patch-diff.githubusercontent.com/raw/serge-sans-paille/pythran/pull/1856.patch',
+    # https://github.com/serge-sans-paille/pythran/pull/1856
-          sha256='18f5e8985d636ad9c73b2f96b601aae299e0c315aa4c0dbee7b2599a63177218',
+    patch('omp.patch', when='@0.9.10:0.9.12')
-          when='@0.9.10:0.9.12')
 
     def patch(self):
         # Compiler is used at run-time to determine name of OpenMP library to search for