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);
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<div class='path'>path: <a href='/guix/commit/?id=94d53fbb07074132c0052e998bb287a7f464b9be'>root</a>/<a href='/guix/commit/gnu?id=94d53fbb07074132c0052e998bb287a7f464b9be'>gnu</a>/<a href='/guix/commit/gnu/bootloader.scm?id=94d53fbb07074132c0052e998bb287a7f464b9be'>bootloader.scm</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='94d53fbb07074132c0052e998bb287a7f464b9be'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Efraim Flashner &lt;efraim@flashner.co.il&gt;</td><td class='right'>2020-03-04 12:00:09 +0200</td></tr>
<tr><th>committer</th><td>Efraim Flashner &lt;efraim@flashner.co.il&gt;</td><td class='right'>2020-03-04 12:00:09 +0200</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/guix/commit/gnu/bootloader.scm?id=94d53fbb07074132c0052e998bb287a7f464b9be'>94d53fbb07074132c0052e998bb287a7f464b9be</a> (<a href='/guix/patch/gnu/bootloader.scm?id=94d53fbb07074132c0052e998bb287a7f464b9be'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/guix/tree/?id=94d53fbb07074132c0052e998bb287a7f464b9be'>a7b34e68a72a1bb5a3648987ddbbf789a76f94d6</a> /<a href='/guix/tree/gnu/bootloader.scm?id=94d53fbb07074132c0052e998bb287a7f464b9be'>gnu/bootloader.scm</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/guix/commit/gnu/bootloader.scm?id=8e38ed1f044a5b42676a35543e452995ac84bc22'>8e38ed1f044a5b42676a35543e452995ac84bc22</a> (<a href='/guix/diff/gnu/bootloader.scm?id=94d53fbb07074132c0052e998bb287a7f464b9be&amp;id2=8e38ed1f044a5b42676a35543e452995ac84bc22'>diff</a>)</td></tr><tr><th>download</th><td colspan='2' class='oid'><a href='/guix/snapshot/guix-94d53fbb07074132c0052e998bb287a7f464b9be.tar.gz'>guix-94d53fbb07074132c0052e998bb287a7f464b9be.tar.gz</a><br/><a href='/guix/snapshot/guix-94d53fbb07074132c0052e998bb287a7f464b9be.zip'>guix-94d53fbb07074132c0052e998bb287a7f464b9be.zip</a><br/></td></tr></table>
<div class='commit-subject'>gnu: editorconfig-vim: Use copy-build-system.</div><div class='commit-msg'>* gnu/packages/vim.scm (editorconfig-vim)[build-system]: Switch to
copy-build-system.
[arguments]: Adjust accordingly.
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