Honor the 'SOURCE_DATE_EPOCH' environment variable to allow for
determinitic builds.

--- a/Lib/py_compile.py
+++ b/Lib/py_compile.py
@@ -105,7 +105,10 @@ def compile(file, cfile=None, dfile=None, doraise=False):
     """
     with open(file, 'U') as f:
         try:
-            timestamp = long(os.fstat(f.fileno()).st_mtime)
+            if 'SOURCE_DATE_EPOCH' in os.environ:
+                timestamp = long(os.environ['SOURCE_DATE_EPOCH'])
+            else:
+                timestamp = long(os.fstat(f.fileno()).st_mtime)
         except AttributeError:
             timestamp = long(os.stat(file).st_mtime)
         codestring = f.read()
diff --git a/Python/import.c b/Python/import.c
index e47ce63..7eecf9c 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -945,6 +945,11 @@ write_compiled_module(PyCodeObject *co, char *cpathname, struct stat *srcstat, t
     /* Now write the true mtime (as a 32-bit field) */
     fseek(fp, 4L, 0);
     assert(mtime <= 0xFFFFFFFF);
+    if (Py_GETENV("SOURCE_DATE_EPOCH") != NULL) {
+	const char *epoch = Py_GETENV("SOURCE_DATE_EPOCH");
+	mtime = atoi(epoch);
+    }
+
     PyMarshal_WriteLongToFile((long)mtime, fp, Py_MARSHAL_VERSION);
     fflush(fp);
     fclose(fp);
ix/tree/build-aux/xgettext.scm?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba'>tree</a><a href='/guix/commit/build-aux/xgettext.scm?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba'>commit</a><a href='/guix/diff/build-aux/xgettext.scm?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/build-aux/xgettext.scm'>
<input type='hidden' name='id' value='bdd141b713b9bcecad09a1ec93a5bb651d340eba'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba'>root</a>/<a href='/guix/log/build-aux?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba'>build-aux</a>/<a href='/guix/log/build-aux/xgettext.scm?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba'>xgettext.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/build-aux/xgettext.scm?id=bdd141b713b9bcecad09a1ec93a5bb651d340eba&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-04-19 16:45:41 +0200'>2024-04-19</span></td><td><a href='/guix/commit/build-aux/xgettext.scm?id=f83b5274c8d67a9bccf8881cc4f87d76a3d172de'>maint: Support `make doc-pot-update' from a tarball.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/xgettext.scm: Move setting of environment variables to shell
header.
(main): Use SOURCE_DATE_EPOCH as fallback for timestamp.  This fixes running
from a tarball.
* Makefile.am (EXTRA_DIST): Add it.

Change-Id: Ic487587b22495868fd2a21545a13dc9e3458299c
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2024-04-14 11:41:41 +0200'>2024-04-14</span></td><td><a href='/guix/commit/build-aux/xgettext.scm?id=e5dda412c2e28fb65a549824f492895e72c33813'>maint: Fix header.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/xgettext.scm: Add `Guix' parts to header.

Change-Id: I4fb03b8b0588f0482bcb1a095518b6751d111031
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2024-04-14 10:29:11 +0200'>2024-04-14</span></td><td><a href='/guix/commit/build-aux/xgettext.scm?id=6c63c366776643e5831c50a2b7e29bad93273327'>maint: Use xgettext.scm wrapper to create .PO files reproducibly.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/xgettext.scm: New script.
* po/guix/Makevars (XGETTEXT): Set it.
(XGETTEXT_OPTIONS): Add --xgettext option to `real' xgettext.
* po/packages/Makevars (XGETTEXT): Set it.
(XGETTEXT_OPTIONS): Add --xgettext option to `real' xgettext.

Change-Id: I71b6b843970090f765f46ac346b92a346560e3f0
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>